National Grid (NGG) 6-K 9 Nov 23 Current report (foreign) Financial data

Cover Page

Cover Page	6 Months Ended
	Sep. 30, 2023
Cover [Abstract]
Amendment Flag	false
Entity Central Index Key	0001004315
Current Fiscal Year End Date	--03-31
Document Period End Date	Sep. 30, 2023
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q2
Entity Registrant Name	NATIONAL GRID PLC
Document Type	6-K

Consolidated income statement

Consolidated income statement - GBP (£) £ in Millions	6 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	[1]
Profit or loss [abstract]
Revenue	£ 8,489	£ 9,444
Provision for bad and doubtful debts	(91)	(52)
Other operating costs	(6,425)	(7,697)
Other operating income	12	544
Operating profit	1,985	2,239
Finance income	115	37
Finance costs	(800)	(661)
Share of post-tax results of joint ventures and associates	71	51
Profit before tax	1,371	1,666
Tax	(307)	(447)
Profit after tax from continuing operations	1,064	1,219	[2]
Profit after tax from discontinued operations	65	37	[2]
Total profit for the period (continuing and discontinued)	1,129	1,256
Attributable to:
Equity shareholders of the parent	1,128	1,256
Non-controlling interests	£ 1	£ 0
Earnings per share (pence)
Basic earnings per share (continuing) (in GBP per share)	£ 0.288	£ 0.334
Diluted earnings per share (continuing) (in GBP per share)	0.287	0.332
Basic earnings per share (continuing and discontinued) (in GBP per share)	0.306	0.344
Diluted earnings per share (continuing and discontinued) (in GBP per share)	£ 0.305	£ 0.342
[1]Comparative amounts have been re-presented to reflect the classification of the Further Acquisition Agreement (the FAA option) as held for sale and within discontinued operations.[2]Comparative amounts have been re-presented to reflect the classification of the FAA option within the UK Gas Transmission business disposal group.

Consolidated statement of compr

Consolidated statement of comprehensive income - GBP (£) £ in Millions	6 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	[1]
Statement of comprehensive income [abstract]
Profit after tax from continuing operations	£ 1,064	£ 1,219	[2]
Profit after tax from discontinued operations	65	37	[2]
Items from continuing operations that will never be reclassified to profit or loss:
Remeasurement losses on pension assets and post-retirement benefit obligations	(263)	(631)
Net (losses)/gains in respect of cash flow hedging of capital expenditure	(2)	14
Tax on items that will never be reclassified to profit or loss	64	159
Total items from continuing operations that will never be reclassified to profit or loss	(201)	(458)
Items from continuing operations that may be reclassified subsequently to profit or loss:
Retranslation of net assets offset by net investment hedge	118	2,360
Exchange differences reclassified to the consolidated income statement on disposal	0	(145)
Net gains in respect of cash flow hedges	201	450
Net gains/(losses) in respect of cost of hedging	40	(64)
Net losses on investments in debt instruments measured at fair value through other comprehensive income	(16)	(47)
Share of other comprehensive income of associates, net of tax	0	1
Tax on items that may be reclassified subsequently to profit or loss	(59)	(86)
Total items from continuing operations that may be reclassified subsequently to profit or loss	284	2,469
Other comprehensive income for the period, net of tax, from continuing operations	83	2,011
Other comprehensive loss for the period, net of tax, from discontinued operations	(9)	(86)
Other comprehensive income for the period, net of tax	74	1,925
Total comprehensive income for the period from continuing operations	1,147	3,230
Total comprehensive income/(loss) for the period from discontinued operations	56	(49)
Total comprehensive income for the period	1,203	3,181
Attributable to:
Equity shareholders of the parent from continuing operations	1,146	3,227
Equity shareholders of the parent from discontinued operations	56	(49)
Equity shareholders of the parent	1,202	3,178
Non-controlling interests	£ 1	£ 3
[1]Comparative amounts have been re-presented to reflect the classification of the FAA option within the UK Gas Transmission business disposal group.[2]Comparative amounts have been re-presented to reflect the classification of the Further Acquisition Agreement (the FAA option) as held for sale and within discontinued operations.

Consolidated statement of chang

Consolidated statement of changes in equity - GBP (£) £ in Millions	Total		Total share-holders’ equity	Share capital	Share premium account	Retained earnings	Other equity reserves	Non-controlling interests
Equity, beginning balance at Mar. 31, 2022	£ 23,856		£ 23,833	£ 485	£ 1,300	£ 26,611	£ (4,563)	£ 23
Profit for the period	1,256	[1]	1,256			1,256
Other comprehensive (loss)/income for the period	1,925	[2]	1,922			(564)	2,486	3
Total comprehensive income for the period	3,181	[2]	3,178			692	2,486	3
Equity dividends	(1,119)		(1,119)			(1,119)
Scrip dividend-related share issue	0		0	1	(1)
Issue of treasury shares	14		14			14
Transactions in own shares	2		2		5	(3)
Share-based payments	20		20			20
Cash flow hedges transferred to the statement of financial position, net of tax	3		3				3
Equity, ending balance at Sep. 30, 2022	25,957		25,931	486	1,304	26,215	(2,074)	26
Equity, beginning balance at Mar. 31, 2023	29,562		29,538	488	1,302	31,608	(3,860)	24
Profit for the period	1,129		1,128			1,128		1
Other comprehensive (loss)/income for the period	74		74			(199)	273
Total comprehensive income for the period	1,203		1,202			929	273	1
Equity dividends	(1,325)		(1,325)			(1,325)
Scrip dividend-related share issue	0		0	1	(1)
Issue of treasury shares	20		20			20
Transactions in own shares	(1)		(1)			(1)
Share-based payments	19		19			19
Cash flow hedges transferred to the statement of financial position, net of tax	2		2				2
Equity, ending balance at Sep. 30, 2023	£ 29,480		£ 29,455	£ 489	£ 1,301	£ 31,250	£ (3,585)	£ 25
[1]Comparative amounts have been re-presented to reflect the classification of the Further Acquisition Agreement (the FAA option) as held for sale and within discontinued operations.[2]Comparative amounts have been re-presented to reflect the classification of the FAA option within the UK Gas Transmission business disposal group.

Consolidated statement of finan

Consolidated statement of financial position - GBP (£) £ in Millions	Sep. 30, 2023	Mar. 31, 2023
Non-current assets
Goodwill	£ 9,905	£ 9,847
Other intangible assets	3,717	3,604
Property, plant and equipment	67,396	64,433
Other non-current assets	570	567
Pension assets	2,352	2,645
Financial and other investments	871	859
Investments in joint ventures and associates	1,414	1,300
Derivative financial assets	325	276
Total non-current assets	86,550	83,531
Current assets
Inventories and current intangible assets	931	876
Trade and other receivables	3,340	3,883
Current tax assets	18	43
Financial and other investments	1,680	2,605
Derivative financial assets	60	153
Cash and cash equivalents	227	163
Assets held for sale	1,441	1,443
Total current assets	7,697	9,166
Total assets	94,247	92,697
Current liabilities
Borrowings	(2,691)	(2,955)
Derivative financial liabilities	(321)	(222)
Trade and other payables	(4,465)	(5,068)
Contract liabilities	(159)	(252)
Current tax liabilities	(231)	(236)
Provisions	(361)	(288)
Liabilities held for sale	(51)	(109)
Total current liabilities	(8,279)	(9,130)
Non-current liabilities
Borrowings	(42,106)	(40,030)
Derivative financial liabilities	(1,116)	(1,071)
Other non-current liabilities	(1,004)	(921)
Contract liabilities	(1,904)	(1,754)
Deferred tax liabilities	(7,318)	(7,181)
Pensions and other post-retirement benefit obligations	(615)	(694)
Provisions	(2,425)	(2,354)
Total non-current liabilities	(56,488)	(54,005)
Total liabilities	(64,767)	(63,135)
Net assets	29,480	29,562
Equity
Share capital	489	488
Share premium account	1,301	1,302
Retained earnings	31,250	31,608
Other equity reserves	(3,585)	(3,860)
Total shareholders’ equity	29,455	29,538
Non-controlling interests	25	24
Total equity	£ 29,480	£ 29,562

Consolidated cash flow statemen

Consolidated cash flow statement - GBP (£) £ in Millions		6 Months Ended
		Sep. 30, 2023	Sep. 30, 2022
Cash flows from operating activities
Operating profit from continuing operations		£ 1,985	£ 2,239	[1]
Adjustments for:
Gain on sale of investments		0	(511)
Other fair value movements		(19)	31
Depreciation, amortisation and impairment		1,021	932
Share-based payments		19	20
Changes in working capital		(10)	(378)
Changes in provisions		39	81
Changes in pensions and other post-retirement benefit obligations		27	(54)
Cash generated from operations – continuing operations		3,062	2,360
Tax paid		(201)	(88)
Net cash flow from operating activities – continuing operations		2,861	2,272
Net cash flow from operating activities – discontinued operations		0	256
Cash flows from investing activities
Purchases of intangible assets		(269)	(224)
Purchases of property, plant and equipment		(3,210)	(3,258)
Disposals of property, plant and equipment		18	63
Investments in joint ventures and associates		(151)	(376)
Dividends received from joint ventures and associates		121	107
Disposal of financial and other investments		65	70
Acquisition of financial investments		(32)	(62)
Net movements in short-term financial investments		885	599
Interest received		69	20
Cash inflows on derivatives		103	0
Cash outflows on derivatives		(4)	(377)
Insurance claim from loss of property, plant and equipment		0	33
Net cash flow used in investing activities – continuing operations		(2,410)	(445)
Net cash flow used in investing activities – discontinued operations		0	(181)
Cash flows from financing activities
Proceeds from issue of treasury shares		20	14
Transactions in own shares		(1)	2
Proceeds received from loans		3,033	9,047
Repayments of loans		(839)	(9,049)
Payments of lease liabilities		(61)	(78)
Net movements in short-term borrowings		(444)	380
Cash inflows on derivatives		68	201
Cash outflows on derivatives		(60)	(230)
Interest paid		(779)	(669)
Dividends paid to shareholders		(1,325)	(1,119)
Net cash flow used in financing activities – continuing operations		(388)	(1,501)
Net cash flow used in financing activities – discontinued operations		0	(334)
Net increase in cash and cash equivalents		63	67
Reclassification to held for sale		0	(5)
Exchange movements		1	15
Net cash and cash equivalents at start of period		163	182
Net cash and cash equivalents at end of period		227	259
The Narragansett Electric Company
Cash flows from investing activities
Disposal of interest in The Narragansett Electric Company	[2]	0	2,968
National Grid Renewables and Emerald Energy Venture LLC
Cash flows from investing activities
Contributions to National Grid Renewables and Emerald Energy Venture LLC		£ (5)	£ (8)
[1]Comparative amounts have been re-presented to reflect the classification of the Further Acquisition Agreement (the FAA option) as held for sale and within discontinued operations.[2]The balance for the period ended 30 September 2022 consists of cash proceeds received, net of cash disposed.

Basis of preparation and new ac

Basis of preparation and new accounting standards, interpretations and amendments	6 Months Ended
	Sep. 30, 2023
Accounting Policies, Changes In Accounting Estimates And Errors [Abstract]
Basis of preparation	1. Basis of preparation and new accounting standards, interpretations and amendments The half year financial information covers the six month periods ended 30 September 2023 and 30 September 2022 and has been prepared in accordance with IAS 34 ‘Interim Financial Reporting’ as issued by the International Accounting Standards Board (IASB). This condensed set of financial statements comprises the unaudited financial information for the half years ended 30 September 2023 and 2022, together with the audited consolidated statement of financial position as at 31 March 2023. The half year financial information has been prepared applying consistent accounting policies to those applied by the Group for the year ended 31 March 2023. The notes to the unaudited financial information are prepared on a continuing basis unless otherwise stated. The financial information for the six months ended 30 September 2023 does not constitute statutory accounts as defined in Section 434 of the Companies Act 2006. It should be read in conjunction with the statutory accounts for the year ended 31 March 2023, which were prepared in accordance with International Financial Reporting Standards (IFRS) as issued by the IASB. The key sources of estimation uncertainty and areas of judgement for the period ended 30 September 2023 are aligned to those disclosed in the Annual Report and Accounts for year ended 31 March 2023, with the following amendments: • whilst the entirety of the UK Electricity System Operator (ESO) is expected to transfer out of the Group to become part of an independent system operator public body, the Independent System Operator and Planner (ISOP), we have concluded that the held for sale criteria were not met as at 30 September 2023 due to the ESO not being available for sale in its present condition given the formation of the ISOP at the half year remained subject to legislative approval. The Group has identified this as an additional area of judgement in the period. The ESO was subsequently classified as held for sale at the end of October 2023 (see note 17); and • the value attributable to GasT TopCo Limited in determining the fair value of the options over the Group’s 40% interests (see note 6) is no longer considered to represent a key source of estimation uncertainty. 1. Basis of preparation and new accounting standards, interpretations and amendments (continued) Going concern As part of the Directors’ consideration of the appropriateness of adopting the going concern basis of accounting in preparing the half year financial information, the Directors have considered the Group’s principal risks (discussed on page 60) alongside potential downside business cash flow scenarios impacting the Group’s operations. The Directors specifically considered both a base case and a reasonable worst-case scenario for business cash flows. The assessment is prepared on the conservative assumption that the Group has no access to the debt capital markets. The main additional cash flow impacts identified in the reasonable worst-case scenario are: • the timing of the sale of assets classified as held for sale; • adverse impacts of inflation and incremental spend on our capital expenditure programme; • adverse impact from timing across the Group (i.e. a net under-recovery of allowed revenues or reductions in over-collections) and slower collections of outstanding receivables; • higher operating and financing costs than expected; including non-delivery of planned efficiencies across the Group; and • the potential impact of further significant storm costs in the US. As part of their analysis, the Board also considered the following potential levers at their discretion to improve the position identified by the analysis if the debt capital markets are not accessible: • the payment of dividends to shareholders; • significant changes in the phasing of the Group’s capital expenditure programme, with elements of non-essential works and programmes delayed; and • a number of further reductions in operating expenditure across the Group. As at 30 September 2023, the Group had undrawn committed facilities available for general corporate purposes amounting to £8.0 billion. Based on these available liquidity resources and having considered the reasonable worst-case scenario, and the further levers at the Board’s discretion, the Group has not identified any material uncertainties relating to events or conditions that, individually or collectively, may cast significant doubt on its ability to continue as a going concern for the foreseeable future, a period not less than 12 months from the date of this report. In addition to the above, the ability to raise new and extend existing financing was separately included in the analysis, and the Directors noted the c.£3.0 billion of new long-term senior debt issued in the period from 1 April to 30 September 2023 as evidence of the Group’s ability to continue to have access to the debt capital markets if needed. Based on the above, the Directors have concluded the Group is well placed to manage its financing and other business risks satisfactorily, and have a reasonable expectation that the Group will have adequate resources to continue in operation for at least 12 months from the signing date of these consolidated interim financial statements. They therefore consider it appropriate to adopt the going concern basis of accounting in preparing the half year financial information. New IFRS accounting standards, interpretations and amendments adopted in the period There are no new standards, interpretations or amendments, issued by the IASB or by the IFRS Interpretations Committee (IFRIC), that are applicable for the period commencing on 1 April 2023 and have had a material impact on the Group’s results. New IFRS accounting standards, interpretations and amendments not yet adopted There are no new accounting standards and amendments to existing standards that have been issued, but are not yet effective that were not disclosed in our Annual Report and Accounts. The Group has not early adopted any standard, amendment or interpretation that has been issued but is not yet effective.
New accounting standards, interpretations and amendments	1. Basis of preparation and new accounting standards, interpretations and amendments The half year financial information covers the six month periods ended 30 September 2023 and 30 September 2022 and has been prepared in accordance with IAS 34 ‘Interim Financial Reporting’ as issued by the International Accounting Standards Board (IASB). This condensed set of financial statements comprises the unaudited financial information for the half years ended 30 September 2023 and 2022, together with the audited consolidated statement of financial position as at 31 March 2023. The half year financial information has been prepared applying consistent accounting policies to those applied by the Group for the year ended 31 March 2023. The notes to the unaudited financial information are prepared on a continuing basis unless otherwise stated. The financial information for the six months ended 30 September 2023 does not constitute statutory accounts as defined in Section 434 of the Companies Act 2006. It should be read in conjunction with the statutory accounts for the year ended 31 March 2023, which were prepared in accordance with International Financial Reporting Standards (IFRS) as issued by the IASB. The key sources of estimation uncertainty and areas of judgement for the period ended 30 September 2023 are aligned to those disclosed in the Annual Report and Accounts for year ended 31 March 2023, with the following amendments: • whilst the entirety of the UK Electricity System Operator (ESO) is expected to transfer out of the Group to become part of an independent system operator public body, the Independent System Operator and Planner (ISOP), we have concluded that the held for sale criteria were not met as at 30 September 2023 due to the ESO not being available for sale in its present condition given the formation of the ISOP at the half year remained subject to legislative approval. The Group has identified this as an additional area of judgement in the period. The ESO was subsequently classified as held for sale at the end of October 2023 (see note 17); and • the value attributable to GasT TopCo Limited in determining the fair value of the options over the Group’s 40% interests (see note 6) is no longer considered to represent a key source of estimation uncertainty. 1. Basis of preparation and new accounting standards, interpretations and amendments (continued) Going concern As part of the Directors’ consideration of the appropriateness of adopting the going concern basis of accounting in preparing the half year financial information, the Directors have considered the Group’s principal risks (discussed on page 60) alongside potential downside business cash flow scenarios impacting the Group’s operations. The Directors specifically considered both a base case and a reasonable worst-case scenario for business cash flows. The assessment is prepared on the conservative assumption that the Group has no access to the debt capital markets. The main additional cash flow impacts identified in the reasonable worst-case scenario are: • the timing of the sale of assets classified as held for sale; • adverse impacts of inflation and incremental spend on our capital expenditure programme; • adverse impact from timing across the Group (i.e. a net under-recovery of allowed revenues or reductions in over-collections) and slower collections of outstanding receivables; • higher operating and financing costs than expected; including non-delivery of planned efficiencies across the Group; and • the potential impact of further significant storm costs in the US. As part of their analysis, the Board also considered the following potential levers at their discretion to improve the position identified by the analysis if the debt capital markets are not accessible: • the payment of dividends to shareholders; • significant changes in the phasing of the Group’s capital expenditure programme, with elements of non-essential works and programmes delayed; and • a number of further reductions in operating expenditure across the Group. As at 30 September 2023, the Group had undrawn committed facilities available for general corporate purposes amounting to £8.0 billion. Based on these available liquidity resources and having considered the reasonable worst-case scenario, and the further levers at the Board’s discretion, the Group has not identified any material uncertainties relating to events or conditions that, individually or collectively, may cast significant doubt on its ability to continue as a going concern for the foreseeable future, a period not less than 12 months from the date of this report. In addition to the above, the ability to raise new and extend existing financing was separately included in the analysis, and the Directors noted the c.£3.0 billion of new long-term senior debt issued in the period from 1 April to 30 September 2023 as evidence of the Group’s ability to continue to have access to the debt capital markets if needed. Based on the above, the Directors have concluded the Group is well placed to manage its financing and other business risks satisfactorily, and have a reasonable expectation that the Group will have adequate resources to continue in operation for at least 12 months from the signing date of these consolidated interim financial statements. They therefore consider it appropriate to adopt the going concern basis of accounting in preparing the half year financial information. New IFRS accounting standards, interpretations and amendments adopted in the period There are no new standards, interpretations or amendments, issued by the IASB or by the IFRS Interpretations Committee (IFRIC), that are applicable for the period commencing on 1 April 2023 and have had a material impact on the Group’s results. New IFRS accounting standards, interpretations and amendments not yet adopted There are no new accounting standards and amendments to existing standards that have been issued, but are not yet effective that were not disclosed in our Annual Report and Accounts. The Group has not early adopted any standard, amendment or interpretation that has been issued but is not yet effective.

Segmental analysis

Segmental analysis	6 Months Ended
	Sep. 30, 2023
Disclosure of operating segments [abstract]
Segmental analysis	2. Segmental analysis Revenue and the results of the business are analysed by operating segment, based on the information the Board use internally for the purposes of evaluating the performance of each operating segment and determining resource allocation between them. The Board is National Grid’s chief operating decision maker (as defined by IFRS 8 ‘Operating Segments’) and assesses the profitability of a profit measure that excludes certain income and expenses. We call that measure ‘adjusted profit’. Adjusted profit excludes exceptional items and remeasurements (as defined in note 4) and is used by management to monitor financial performance as it is considered that it aids the comparability of our reported financial performance from year to year. As a matter of course, the Board also considers profitability by segment, excluding the effect of major storms and timing adjustments relating to revenue and certain pass-through costs. However, the measure of profit disclosed in this note is operating profit before exceptional items and remeasurements, as this is the measure that is most consistent with the IFRS results reported within these financial statements. In the year ended 31 March 2023, the National Grid Ventures (NGV) operating segment met the quantitative thresholds set out in IFRS 8 to be identified as the Group’s sixth separate reportable segment. Accordingly, the Group’s operating segments were modified and the data relating to previous periods has been restated to reflect this change. The results of our six principal businesses are reported to the Board and are accordingly treated as reportable operating segments. All other operating segments are either reported to the Board on an aggregated basis or do not meet the quantitative threshold in order to be considered a separate operating segment. The following table describes the main activities for each reportable operating segment: UK Electricity Transmission The high-voltage electricity transmission networks in England and Wales. This includes our Accelerated Strategic Transmission Investment projects to connect more clean, low-carbon power to the transmission network in England and Wales. UK Electricity Distribution The electricity distribution networks of NGED in the East Midlands, West Midlands and South West of England and South Wales. UK Electricity System Operator The Great Britain system operator. The ESO has not met the criteria to be classified as held for sale as at 30 September 2023. New England Gas distribution networks, electricity distribution networks and high-voltage electricity transmission networks in New England. New York Gas distribution networks, electricity distribution networks and high-voltage electricity transmission networks in New York. National Grid Ventures Comprises all commercial operations in LNG at the Isle of Grain in the UK and Providence, Rhode Island in the US, our electricity generation business in the US, our electricity interconnectors in the UK and our investment in National Grid Renewables Development LLC, our renewables business in the US. NGV operates outside our regulated core business. Our US LNG operations were reclassified from the New England segment following an internal reorganisation in the period. The New England and New York segments typically experience seasonal fluctuations in revenue and operating profit due to higher delivery volumes during the second half of the financial year, for example as a result of colder weather over the winter months driving increased heating demand. These seasonal fluctuations have a consequential impact on the working capital balances (primarily trade debtors and accrued income) in the consolidated statement of financial position at 30 September 2023 when compared to 31 March 2023. The majority of UK revenues are derived from the supply of network capacity rather than the supply of commodities and therefore are not subject to the same seasonal fluctuations as in New York and New England. Other activities that do not form part of any of the segments in the above table primarily relate to our UK property business together with insurance and corporate activities in the UK and US and the Group’s investments in technology and innovation companies through National Grid Partners. 2. Segmental analysis (continued) (a) Revenue Six months ended 30 September 2023 2022² Total sales Sales between segments 1 Sales to third parties Total sales Sales between segments 1 Sales to third £m £m £m £m £m £m Operating segments – continuing operations: UK Electricity Transmission 1,356 (19) 1,337 969 (14) 955 UK Electricity Distribution 850 (2) 848 1,005 (8) 997 UK Electricity System Operator 1,734 (17) 1,717 2,060 (15) 2,045 New England 1,441 — 1,441 1,760 — 1,760 New York 2,365 — 2,365 2,758 — 2,758 National Grid Ventures 666 (27) 639 685 (9) 676 Other 142 — 142 253 — 253 Total revenue from continuing operations 8,554 (65) 8,489 9,490 (46) 9,444 Geographical areas: UK 4,309 4,589 US 4,180 4,855 Total revenue from continuing operations 8,489 9,444 1. Sales between operating segments are priced having regard to the regulatory and legal requirements to which the businesses are subject. The analysis of revenue by geographical area is on the basis of destination. There are no material sales between the UK and US geographical areas. 2. Comparative amounts have been re-presented to reflect NGV as a separate operating segment. (b) Operating profit/(loss) Before exceptional items and remeasurements Exceptional items and remeasurements (see note 4) After exceptional items and remeasurements Six months ended 30 September 2023 2022¹ 2023 2022¹ 2023 2022¹ £m £m £m £m £m £m Operating segments – continuing operations: UK Electricity Transmission 839 499 (1) (6) 838 493 UK Electricity Distribution 476 531 (4) (9) 472 522 UK Electricity System Operator 443 147 — (1) 443 146 New England (32) 193 (15) 527 (47) 720 New York (30) (18) 38 (8) 8 (26) National Grid Ventures 219 259 91 49 310 308 Other (13) 145 (26) (69) (39) 76 Total operating profit from continuing operations 1,902 1,756 83 483 1,985 2,239 Geographical areas: UK 1,956 1,550 60 (32) 2,016 1,518 US (54) 206 23 515 (31) 721 Total operating profit from continuing operations 1,902 1,756 83 483 1,985 2,239 1. Comparative amounts have been re-presented to reflect NGV as a separate operating segment. Before exceptional items and remeasurements Exceptional items and remeasurements (see note 4) After exceptional items and remeasurements Six months ended 30 September 2023 2022¹ 2023 2022¹ 2023 2022¹ £m £m £m £m £m £m Reconciliation to profit before tax: Operating profit from continuing operations 1,902 1,756 83 483 1,985 2,239 Share of post-tax results of joint ventures and associates 59 70 12 (19) 71 51 Finance income 123 69 (8) (32) 115 37 Finance costs (834) (801) 34 140 (800) (661) Total profit before tax from continuing operations 1,250 1,094 121 572 1,371 1,666 1. Comparative amounts have been re-presented to reflect the classification of the FAA option as held for sale and within discontinued operations. 2. Segmental analysis (continued) (c) Capital expenditure Capital expenditure represents additions to property, plant and equipment and other intangible assets but excludes additional investments in and loans to joint ventures and associates. Net book value of property, plant and equipment and other intangible assets Capital expenditure Depreciation, amortisation 30 September 2023 31 March 2023¹ 30 September 2023 30 September 2022¹ 30 September 2023 30 September 2022¹ £m £m £m £m £m £m Operating segments: UK Electricity Transmission 16,030 15,483 800 629 (250) (235) UK Electricity Distribution 13,940 13,462 608 584 (105) (104) UK Electricity System Operator 434 411 75 42 (52) (40) New England 13,781 13,033 789 801 (204) (184) New York 22,937 21,730 1,257 1,242 (321) (292) National Grid Ventures 3,956 3,880 175 410 (84) (73) Other 35 38 2 9 (5) (4) Total 71,113 68,037 3,706 3,717 (1,021) (932) Geographical areas: UK 33,475 32,343 1,649 1,594 (464) (432) US 37,638 35,694 2,057 2,123 (557) (500) Total 71,113 68,037 3,706 3,717 (1,021) (932) By asset type: Property, plant and equipment 67,396 64,433 3,449 3,490 (868) (829) Other intangible assets 3,717 3,604 257 227 (153) (103) Total 71,113 68,037 3,706 3,717 (1,021) (932) 1. Comparative amounts have been re-presented to reflect NGV as a separate operating segment and the reclassification of our US LNG operations from New England to NGV following an internal reorganisation in the period.

Revenue

Revenue	6 Months Ended
	Sep. 30, 2023
Revenue [abstract]
Revenue	3. Revenue Under IFRS 15 ‘Revenue from Contracts with Customers’, revenue is recorded as or when the Group satisfies a performance obligation by transferring a promised good or service to a customer. A good or service is transferred when the customer obtains control of that good or service. The transfer of control of our distribution or transmission services coincides with the use of our network, as electricity and gas pass through our network and reach our customers. The Group principally satisfies its performance obligations over time and the amount of revenue recorded corresponds to the amounts billed and accrued for volumes of gas and electricity delivered/transferred to/from our customers. Revenue for the six months ended 30 September 2023 UK Electricity Transmission UK Electricity Distribution UK Electricity System Operator New New National Grid Ventures Other Total Revenue under IFRS 15 Transmission 1,299 — 5 43 283 426 — 2,056 Distribution — 810 — 1,329 2,047 — — 4,186 System Operator — — 1,712 — — — — 1,712 Other 1 9 36 — 4 7 75 — 131 Total IFRS 15 revenue 1,308 846 1,717 1,376 2,337 501 — 8,085 Other revenue Generation — — — — — 181 — 181 Other 2 29 2 — 65 28 (43) 142 223 Total other revenue 29 2 — 65 28 138 142 404 Total revenue from continuing operations 1,337 848 1,717 1,441 2,365 639 142 8,489 Geographic split of revenue for the six months ended 30 September 2023 UK Electricity Transmission UK Electricity Distribution UK Electricity System Operator New England New National Grid Ventures Other Total Revenue under IFRS 15 UK 1,308 846 1,717 — — 430 — 4,301 US — — — 1,376 2,337 71 — 3,784 Total IFRS 15 revenue 1,308 846 1,717 1,376 2,337 501 — 8,085 Other revenue UK 29 2 — — — (50) 27 8 US — — — 65 28 188 115 396 Total other revenue 29 2 — 65 28 138 142 404 Total revenue from continuing operations 1,337 848 1,717 1,441 2,365 639 142 8,489 1. The UK Electricity Transmission and UK Electricity Distribution other IFRS 15 revenue principally relates to engineering recharges, which are the recovery of costs incurred for construction work requested by customers, such as the re-routing of existing network assets. Within NGV, the other IFRS 15 revenue principally relates to revenue generated from our NG Renewables business. 2. Other revenue, recognised in accordance with accounting standards other than IFRS 15, includes property sales by our UK commercial property business, rental income, income arising in connection with the Transition Services Agreements in place following the sales of The Narragansett Electric Company (NECO) and the UK Gas Transmission business, and an adjustment to NGV revenue in respect of the interconnector cap and floor and Use of Revenue regimes constructed by Ofgem. 3. Revenue (continued) Revenue for the six months ended 30 September 2022 UK Electricity Transmission UK Electricity Distribution UK Electricity System Operator New England New York National Grid Ventures¹ £m Other¹ £m Total Revenue under IFRS 15 Transmission 931 — 77 53 117 306 — 1,484 Distribution — 940 — 1,675 2,617 — — 5,232 System Operator — — 1,968 — — — — 1,968 Other 2 16 43 — 4 6 69 — 138 Total IFRS 15 revenue 947 983 2,045 1,732 2,740 375 — 8,822 Other revenue Generation — — — — — 224 — 224 Other 3 8 14 — 28 18 77 253 398 Total other revenue 8 14 — 28 18 301 253 622 Total revenue from continuing operations 955 997 2,045 1,760 2,758 676 253 9,444 Geographic split of revenue for the six months ended 30 September 2022 UK Electricity Transmission UK Electricity Distribution UK Electricity System Operator New England New York National Grid Ventures¹ £m Other¹ £m Total Revenue under IFRS 15 UK 947 983 2,045 — — 310 — 4,285 US — — — 1,732 2,740 65 — 4,537 Total IFRS 15 revenue 947 983 2,045 1,732 2,740 375 — 8,822 Other revenue UK 8 14 — — — 83 199 304 US — — — 28 18 218 54 318 Total other revenue 8 14 — 28 18 301 253 622 Total revenue from continuing operations 955 997 2,045 1,760 2,758 676 253 9,444 1. Comparative amounts have been re-presented to reflect NGV as a separate operating segment. 2. The UK Electricity Transmission and UK Electricity Distribution other IFRS 15 revenue principally relates to engineering recharges, which are the recovery of costs incurred for construction work requested by customers, such as the re-routing of existing network assets. Within NGV, the other IFRS 15 revenue principally relates to revenue generated from our NG Renewables business.

Exceptional items and remeasure

Exceptional items and remeasurements	6 Months Ended
	Sep. 30, 2023
Exceptional Items And Remeasurements [Abstract]
Exceptional items and remeasurements	4. Exceptional items and remeasurements To monitor our segmental financial performance, we use an adjusted consolidated profit measure that excludes certain income and expenses. We exclude items from adjusted profit because, if included, these items could distort understanding of our performance in the period and the comparability between periods. With respect to restructuring costs, these represent additional expenses incurred that are not related to normal business and day‑to-day activities. These can take place over multiple reporting periods given the scale of the Group, the nature and complexity of the transformation initiatives and due to the impact of strategic transactions. Remeasurements comprise unrealised gains or losses recorded in the consolidated income statement arising from changes in the fair value of certain financial assets and liabilities categorised as held at fair value through profit and loss (FVTPL). Once the fair value movements are realised (for example, when the derivative matures), the previously recognised fair value movements are then reversed through remeasurements and recognised within earnings before exceptional items and remeasurements. These assets and liabilities include commodity contracts and derivative financial instruments to the extent that hedge accounting is either not achieved or is not effective. We have also classified the unrealised gains or losses reported in profit and loss on certain additional assets treated as FVTPL within remeasurements. These relate to financial assets (which fail the ‘solely payments of principal and interest test’ under IFRS 9), the money market fund investments used by Group Treasury for cash management purposes and the net foreign exchange gains and losses on borrowing activities. These are offset by foreign exchange losses and gains on financing derivatives measured at fair value. In all cases, these fair values increase or decrease because of changes in foreign exchange, commodity or other financial indices over which we have no control. Six months ended 30 September 2023 Exceptional items Remeasurements Total Included within operating profit from continuing operations Cost efficiency programme (39) — (39) Transaction, separation and integration costs¹ (11) — (11) IFA1 fire insurance proceeds 92 — 92 Net gains on commodity contract derivatives — 41 41 42 41 83 Six months ended 30 September 2022² Exceptional items Remeasurements Total Included within operating profit from continuing operations Net gain on disposal of NECO 511 — 511 Cost efficiency programme (61) — (61) Transaction, separation and integration costs 1 (65) — (65) IFA1 fire insurance proceeds 33 — 33 Net gains on commodity contract derivatives — 65 65 418 65 483 1. Transaction, separation and integration costs represent the aggregate of distinct activities undertaken by the Group in the periods presented. 2. Comparative amounts have been re-presented to reflect the classification of the FAA option as held for sale and within discontinued operations. Cost efficiency programme: During the period, the Group incurred a further £39 million (2022: £61 million) of costs in relation to the major cost efficiency programme announced in November 2021, that targeted at least £400 million savings per annum across the Group by the end of three years. The costs recognised in the period primarily relate to redundancy provisions, employee costs and professional fees incurred in delivering the programme. Whilst the costs incurred during the period do not meet the quantitative threshold to be classified as exceptional on a standalone basis, when taken in aggregate with the £142 million of costs incurred since the announcement of the programme, the costs qualify for exceptional treatment in line with our exceptional items policy. Estimated costs expected to be incurred over the remainder of the programme to 31 March 2024 remain consistent with those disclosed in the Annual Report and Accounts for year the ended 31 March 2023. The total cash outflow for the period in relation to these costs was £28 million (2022: £38 million). Transaction, separation and integration costs: During the period, £11 million (2022: £65 million) of transaction and separation costs were incurred in relation to the disposals of NECO and the UK Gas Transmission business (see note 6) and the integration of NGED. The costs incurred primarily relate to legal fees, professional fees, and employee costs. The costs have been classified as exceptional, consistent with similar costs for the year ended 31 March 2023 and past precedent. The total cash outflow for the period in relation to these costs was £9 million (2022: £59 million). 4. Exceptional items and remeasurements (continued) IFA1 interconnector insurance recovery: In September 2021, a fire at the IFA1 converter station in Sellindge, Kent caused significant damage to infrastructure on-site. In the period, the Group recognised net insurance claims of £92 million (2022: £33 million) which were recognised as exceptional in line with our exceptional items policy and consistent with related claims in the prior year. The total cash inflow in the period in relation to the property damage insurance proceeds was £nil (2022: £33 million). Net gain on disposal of NECO: During the prior period, the Group recognised a gain of £511 million on the disposal of 100% of the share capital of NECO to PPL Rhode Island Holdings, LLC for cash consideration of £3.1 billion ($3.9 billion). The receipt of cash was recognised within net cash used in investing activities within the consolidated cash flow statement. Details of remeasurements, tax exceptional items and the tax effect of exceptional items and remeasurements are also provided in this note. Six months ended 30 September 2023 Exceptional items Remeasurements Total Included within operating profit from continuing operations 42 41 83 Included within net finance costs (note 5) Net gains on derivative financial instruments — 34 34 Net losses on financial assets at fair value through profit and loss — (8) (8) — 26 26 Included within share of post-tax results of joint ventures and associates Net gains on financial instruments — 12 12 — 12 12 Total included within profit before tax from continuing operations 42 79 121 Tax on exceptional items and remeasurements 1 (21) (20) Total exceptional items and remeasurements after tax from 43 58 101 Six months ended 30 September 2022¹ Exceptional items Remeasurements Total Included within operating profit from continuing operations 418 65 483 Included within net finance costs (note 5) Net gains on derivative financial instruments — 140 140 Net losses on financial assets at fair value through profit and loss — (32) (32) — 108 108 Included within share of post-tax results of joint ventures and associates Net losses on financial instruments — (19) (19) — (19) (19) Total included within profit before tax from continuing operations 418 154 572 Tax on exceptional items and remeasurements (221) (49) (270) Total exceptional items and remeasurements after tax from 197 105 302 1. Comparative amounts have been re-presented to reflect the classification of the FAA option as held for sale and within discontinued operations.

Finance income and costs

Finance income and costs	6 Months Ended
	Sep. 30, 2023
Analysis of income and expense [abstract]
Finance income and costs	5. Finance income and costs 2023 2022¹ Six months ended 30 September Notes £m £m Finance income Interest income from financing activities 52 14 Net interest on pensions and other post-retirement benefit obligations 51 41 Net losses on financial assets at fair value through profit and loss (8) (32) Other interest income 20 14 115 37 Finance costs Interest expense on financial instruments 2 (903) (878) Unwinding of discount on provisions (50) (42) Other interest (8) 8 Net gains on derivative financial instruments 3 34 140 Less: interest capitalised 4 127 111 (800) (661) Net finance costs (685) (624) 1. Comparative amounts have been re-presented to reflect the classification of the FAA option as held for sale and within discontinued operations. 2. Finance costs include principal accretion on inflation-linked debt of £149 million (2022: £240 million) and income related to principal accretion on inflation-linked swaps of £18 million (2022: £5 million expense). 3. Includes a net foreign exchange gain on borrowing activities, offset by foreign exchange losses and gains on financing derivatives measured at fair value.

Assets held for sale and discon

Assets held for sale and discontinued operations	6 Months Ended
	Sep. 30, 2023
Non-current assets or disposal groups classified as held for sale or as held for distribution to owners [abstract]
Assets held for sale and discontinued operations	6. Assets held for sale and discontinued operations Assets and businesses are classified as held for sale when their carrying amounts are recovered through sale rather than through continuing use. They only meet the held for sale condition when the assets are ready for immediate sale in their present condition, management is committed to the sale and it is highly probable that the sale will complete within one year. Depreciation ceases on assets and businesses when they are classified as held for sale and the assets and businesses are impaired if their carrying value exceeds their fair value less expected costs to sell. The results and cash flows of assets or businesses classified as held for sale or sold during the year, that meet the criteria of being a major separate line of business or geographical area of operation, are shown separately from our continuing operations, and presented within discontinued operations in the income statement and cash flow statement. The following assets and liabilities were classified as held for sale: 30 September 2023 31 March 2023 Total assets Total liabilities held for sale Net assets held for sale Total assets Total liabilities held for sale Net assets held for sale Investment in GasT TopCo Limited 1,441 — 1,441 1,443 — 1,443 FAA option — — — — (109) (109) FAA forward — (7) (7) — — — RAA option — (44) (44) — — — Net assets held for sale 1,441 (51) 1,390 1,443 (109) 1,334 On 31 January 2023, the Group disposed of 100% of the UK Gas Transmission business for cash consideration of £4.0 billion and a 40% interest in a newly incorporated UK limited company, GasT TopCo Limited. The other 60% was purchased by Macquarie Infrastructure and Real Assets (MIRA) and British Columbia Investment Management Corporation (BCI) (together, the ‘Consortium’). The Group also entered into a Further Acquisition Agreement (the FAA option) with the Consortium over its remaining 40% interest. The Group’s interest in GasT TopCo Limited was immediately classified as held for sale with effect from 31 January 2023 together with the FAA option, as detailed in note 10 of the Annual Report and Accounts for the year ended 31 March 2023. The Group has not applied equity accounting in relation to its investment in GasT TopCo Limited. On 19 July 2023, following the partial exercise of the FAA option by the Consortium, the Group agreed to sell a further 20% out of the remaining 40% interests in GasT TopCo Limited (the FAA forward). Completion is expected in the second half of calendar year 2023, subject to regulatory approval. As part of the transaction, the Group entered into a new option agreement with the Consortium, the Remaining Acquisition Agreement (the RAA option), to replace the FAA option for the potential sale of all or part of the remaining 20% equity interest in GasT TopCo Limited. The RAA option is exercisable, at the Consortium’s option, between 1 May 2024 and 31 July 2024. If the RAA option is partially exercised by the Consortium, the Group will have the right to put the remainder of its interests in GasT TopCo Limited to the Consortium, which can be exercised by the Group between 1 December 2024 and 31 December 2024. The FAA forward to complete the sale of 20% of GasT TopCo Limited is a Level 3 derivative and some of the assumptions which are used to determine the fair value are specific to the contract and not readily observable in active markets. The most significant unobservable input is the valuation of GasT TopCo Limited’s unlisted equity. The RAA option is also a Level 3 derivative. Significant unobservable inputs include the valuation and volatility of GasT TopCo Limited’s unlisted equity. These inputs are used as part of a Black-Scholes option pricing model to provide the reported fair values. The disposal of the Group’s interests in GasT TopCo Limited is considered to be the final stage of the plan to dispose of the UK Transmission business first announced in 2021. As a result, the results of the business prior to the recognition of the associate and any remeasurements pertaining to the financial derivatives noted above are shown separately from the continuing business for all periods presented on the face of the income statement as a discontinued operation. This is also reflected in the statement of comprehensive income, as well as earnings per share (EPS) being shown split between continuing and discontinued operations. 6. Assets held for sale and discontinued operations (continued) The summary income statements for the periods ended 30 September 2023 and 2022 are as follows: 2023 2022¹ £m £m Discontinued operations Revenue — 805 Other operating costs — (459) Operating profit — 346 Finance income 9 9 Finance costs² 61 (261) Profit/(loss) before tax 70 94 Tax (5) (57) Profit/(loss) after tax from discontinued operations 65 37 1. Comparative amounts have been re-presented to reflect the classification of the FAA option as held for sale and within discontinued operations. 2. Finance costs include the remeasurement of the FAA option, the FAA forward and the RAA option. The summary statements of comprehensive income are as follows: 2023 2022¹ £m £m Profit after tax from discontinued operations 65 37 Other comprehensive (loss)/income from discontinued operations Items from discontinued operations that will never be reclassified to profit or loss: Remeasurement losses on pension assets and post-retirement benefit obligations — (126) Tax on items that will never be reclassified to profit or loss — 31 Total losses from discontinued operations that will never be reclassified to profit or loss — (95) Items from discontinued operations that may be reclassified subsequently to profit or loss: Net gains in respect of cash flow hedges — 8 Net gains in respect of cost of hedging — 4 Net losses on investments in debt instruments measured at fair value through other (12) — Tax on items that may be reclassified subsequently to profit or loss 3 (3) Total (losses)/gains from discontinued operations that may be reclassified subsequently to profit or loss (9) 9 Other comprehensive loss for the period, net of tax, from discontinued operations (9) (86) Total comprehensive income/(loss) for the period from discontinued operations 56 (49) 1. Comparative amounts have been re-presented to reflect the classification of the FAA option as held for sale and within discontinued operations.

Tax from continuing operations

Tax from continuing operations	6 Months Ended
	Sep. 30, 2023
Income taxes paid (refund) [abstract]
Tax from continuing operations	7. Tax from continuing operations The tax charge from continuing operations for the six month period ended 30 September 2023 is £307 million (2022: £447 million). It is based on management’s estimate of the weighted average effective tax rate by jurisdiction expected for the full year. The effective tax rate is 22.4% (2022: 26.8%), which includes the impact of our share of post-tax results of joint ventures and associates. The effective tax rate for the year ended 31 March 2023 was 24.4% including the impact of our share of post-tax results of joint ventures and associates. The legislation implementing the Organisation for Economic Co-operation and Development’s (OECD) proposals for a global minimum corporation tax rate (‘Pillar 2’) was enacted into UK law on 11 July 2023. The legislation includes an income inclusion rule and a domestic minimum tax, which together are designed to ensure a minimum effective tax rate of 15% in each country in which the Group operates. Similar legislation is being enacted by other governments around the world. The legislation is effective for National Grid from 1 April 2024 and therefore the rules do not impact the Group’s consolidated financial statements for year ended 31 March 2024. We have applied the mandatory exception in the UK to recognising and disclosing information about the deferred tax assets and liabilities related to Pillar 2 income taxes in accordance with the amendments to IAS 12 published by the IASB on 23 May 2023. The Group’s work is ongoing to assess the potential impact in the financial statements for year ended 31 March 2025.

Earnings per share

Earnings per share	6 Months Ended
	Sep. 30, 2023
Earnings per share [abstract]
Earnings per share	8. Earnings per share The earnings per share (EPS) calculations are based on profit after tax attributable to equity shareholders of the parent company which excludes non-controlling interests. (a) Basic earnings per share Earnings EPS Earnings EPS Six months ended 30 September 2023 2023 2022¹ 2022¹ £m pence £m pence Profit after tax from continuing operations attributable to the parent 1,063 28.8 1,219 33.4 Profit after tax from discontinued operations attributable to the parent 65 1.8 37 1 Total profit after tax attributable to the parent 1,128 30.6 1,256 34.4 2023 2022 millions millions Weighted average number of shares – basic 3,682 3,651 1. Comparative amounts have been re-presented to reflect the classification of the FAA option as held for sale and within discontinued operations. (b) Diluted earnings per share Earnings EPS Earnings EPS Six months ended 30 September 2023 2023 2022¹ 2022¹ £m pence £m pence Profit after tax from continuing operations attributable to the parent 1,063 28.7 1,219 33.2 Profit after tax from discontinued operations attributable to the parent 65 1.8 37 1 Total profit after tax attributable to the parent 1,128 30.5 1,256 34.2 2023 2022 millions millions Weighted average number of shares – diluted 3,700 3,668 1. Comparative amounts have been re-presented to reflect the classification of the FAA option as held for sale and within discontinued operations.

Dividends

Dividends	6 Months Ended
	Sep. 30, 2023
Subclassifications of assets, liabilities and equities [abstract]
Dividends	9. Dividends Pence Cash Scrip Ordinary dividends Final dividend in respect of the year ended 31 March 2023 37.60 1,325 56 Interim dividend in respect of the year ended 31 March 2023 17.84 488 163 Final dividend in respect of the year ended 31 March 2022 33.76 1,119 114 The Directors are proposing an interim dividend of 19.40 pence per share to be paid in respect of the year ending 31 March 2024. This would absorb £716 million of shareholders’ equity.

Fair value measurement

Fair value measurement	6 Months Ended
	Sep. 30, 2023
Fair Value Measurement [Abstract]
Fair value measurement	10. Fair value measurement Assets and liabilities measured at fair value Included in the statement of financial position are certain financial assets and liabilities which are measured at fair value. The following table categorises these assets and liabilities by the valuation methodology applied in determining their fair value using the fair value hierarchy described on page 197 of the Annual Report and Accounts for the year ended 31 March 2023. 30 September 2023 31 March 2023 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Investments held at fair value through profit and loss 1,007 — 483 1,490 1,764 — 452 2,216 Investments held at fair value through other comprehensive income 1 — 388 — 388 — 407 — 407 Financing derivatives — 309 20 329 — 341 22 363 Commodity contract derivatives — 54 2 56 — 62 4 66 1,007 751 505 2,263 1,764 810 478 3,052 Liabilities Financing derivatives — (1,219) (95) (1,314) — (997) (122) (1,119) Commodity contract derivatives — (78) (45) (123) — (134) (40) (174) Contingent consideration 2 — — (10) (10) — — (19) (19) — (1,297) (150) (1,447) — (1,131) (181) (1,312) Total 1,007 (546) 355 816 1,764 (321) 297 1,740 1. Investments held include instruments which meet the criteria of IFRS 9 or IAS 19. 2. Contingent consideration relates to the acquisition of National Grid Renewables Development LLC. The estimated fair value of total borrowings, excluding lease liabilities, using market values at 30 September 2023 is £38,354 million (31 March 2023: £38,219 million). Our level 1 financial investments and liabilities held at fair value are valued using quoted prices from liquid markets and primarily comprise investments in short-term money market funds. Our level 2 financial investments held at fair value primarily include bonds with a tenor greater than one year and are valued using quoted prices for similar instruments in active markets, or quoted prices for identical or similar instruments in inactive markets. Alternatively, they are valued using models where all significant inputs are based directly or indirectly on observable market data. 10. Fair value measurement (continued) Our level 2 financing derivatives include cross-currency, interest rate and foreign exchange derivatives. We value these derivatives by discounting all future cash flows by externally sourced market yield curves at the reporting date, taking into account the credit quality of both parties. These derivatives can be priced using liquidly traded interest rate curves and foreign exchange rates, and therefore we classify our vanilla trades as level 2 under the IFRS 13 framework. Our level 2 commodity derivatives include over-the-counter gas swaps and power swaps as well as forward physical gas deals. We value our contracts based on market data obtained from the New York Mercantile Exchange (NYMEX) and the Intercontinental Exchange (ICE) where forward monthly prices are available. We discount based on externally sourced market yield curves at the reporting date, taking into account the credit quality of both parties and liquidity in the market. Our commodity contracts can be priced using liquidly traded swaps. Therefore we classify our vanilla trades as level 2 under the IFRS 13 framework. Our level 3 financing derivatives include inflation-linked swaps, where the market is illiquid. In valuing these instruments we use in-house valuation models and obtain external valuations to support each reported fair value. Our level 3 commodity contract derivatives primarily consist of our forward purchases of electricity and gas that we value using proprietary models. Derivatives are classified as Level 3 where significant inputs into the valuation technique are neither directly nor indirectly observable (including our own data, which are adjusted, if necessary, to reflect the assumptions market participants would use in the circumstances). Our level 3 investments include equity instruments accounted for at fair value through profit and loss. These equity holdings are part of our corporate venture capital portfolio held by National Grid Partners and comprise a series of relatively small, early-stage non-controlling minority interest unquoted investments where prices or valuation inputs are unobservable. Fifteen equity investments (out of thirty-three) are fair valued based on the latest transaction price (a price within the last 12 months), either being the price we paid for the investments, marked to a latest round of funding and adjusted for our preferential rights or based on an internal model. In addition, we have eighteen investments without a transaction in the last 12 months that underwent an internal valuation process using the Black-Scholes Murton Option Pricing Model (OPM Backsolve). Between 12 and 18 months a blend between OPM Backsolve and other techniques are utilised such as proxy group revenue multiples, discounted cash flow, comparable company analysis and probability weighted expected return approach in order to triangulate a valuation. After 18 months the valuation is based on these alternative methods as the last fundraising price is no longer a reliable basis for valuation. Our level 3 investments also include our investment in Sunrun Neptune 2016 LLC, which is accounted for at fair value through profit and loss. The investment is fair valued by discounting expected cash flows using a weighted average cost of capital specific to Sunrun Neptune 2016 LLC. 10. Fair value measurement (continued) The impacts on a post-tax basis of reasonably possible changes in significant assumptions used in valuing assets and liabilities classified within level 3 of the fair value hierarchy are as follows: Financing derivatives Commodity contract derivatives Other Six months ended 30 September 2023 2022 2023 2022 2023 2022 £m £m £m £m £m £m 10% increase in commodity prices — — 15 35 — — 10% decrease in commodity prices — — (15) (36) — — +10% market area price change — — 12 7 — — -10% market area price change — — (11) (7) — — +20 basis point increase in Limited Price Index (38) (51) — — — — -20 basis point decrease in LPI market curve 38 51 — — — — +20 basis point increase between Retail Price Index (RPI) and Consumer Price Index (CPI) 36 17 — — — — -20 basis point decrease between RPI and CPI market curves (33) (16) — — — — +50 basis points change in discount rate — — — — (8) (9) -50 basis points change in discount rate — — — — 9 10 +10% change in venture capital price — — — — 30 — -10% change in venture capital price — — — — (30) — The impacts disclosed above were considered on a contract by contract basis with the most significant unobservable inputs identified. A reasonably possible change in assumptions for other level 3 assets and liabilities would not result in a material change in fair values. The changes in fair value of our level 3 financial assets and liabilities in the six months to 30 September are presented below: Financing derivatives Commodity contract derivatives Other 1 Total 2023 2022 2023 2022 2023 2022 2023 2022 £m £m £m £m £m £m £m £m At 1 April (100) (187) (36) 44 433 376 297 233 Net gains/(losses) through the consolidated income statement for the period 2,3 25 76 (4) 44 26 30 47 150 Purchases — (133) (10) (56) 11 37 1 (152) Settlements — — 7 (4) 3 (4) 10 (8) At 30 September 4 (75) (244) (43) 28 473 439 355 223 1. Other comprises our investments in Sunrun Neptune 2016 LLC and the investments made by National Grid Partners, which are accounted for at fair value through profit and loss and the contingent consideration arising from the acquisition of National Grid Renewables Development LLC. Net gains and loss are recognised within finance income and costs in the income statement. 2. Gains of £25 million (2022: gains of £93 million) are attributable to derivative financial instruments held at the end of the reporting period and have been recognised in finance costs in the income statement. 3. Losses of £15 million (2022: losses of £23 million) are attributable to the commodity contract derivative financial instruments held at the end of the reporting period and have been recognised in other operating costs in the consolidated income statement. 4. There were no reclassifications in or out of level 3 (2022: none). The Group also has a number of financial instruments which are not measured at fair value in the balance sheet. The carrying value of current financial assets at amortised cost approximates their fair values, primarily due to short-dated maturities.

Net debt

Net debt	6 Months Ended
	Sep. 30, 2023
Subclassifications of assets, liabilities and equities [abstract]
Net debt	11. Net debt Net debt is comprised as follows: 30 September 2023 31 March 2023 £m £m Cash and cash equivalents 227 163 Current financial investments 1,680 2,605 Borrowings and bank overdrafts (44,797) (42,985) Financing derivatives 1 (985) (756) Net debt (net of related derivative financial instruments) (43,875) (40,973) 1. Includes £4 million liability (31 March 2023: £4 million liability) in relation to the hedging of capital expenditure. The cash flows related to these derivatives are included within investing activities in the consolidated cash flow statement which is in the same manner as the transactions which are the subject of the hedges. The financing derivatives balance included in net debt exclude the commodity derivatives. The following table splits out the total derivative balances on the face of the consolidated statement of financial position by category: 30 September 2023 31 March 2023 Assets Liabilities Total Assets Liabilities Total Financing derivatives 329 (1,314) (985) 363 (1,119) (756) Commodity contract derivatives 56 (123) (67) 66 (174) (108) Total derivative financial instruments 385 (1,437) (1,052) 429 (1,293) (864)

Pensions and other post-retirem

Pensions and other post-retirement benefit obligations	6 Months Ended
	Sep. 30, 2023
Employee Benefits [Abstract]
Pensions and other post-retirement benefit obligations	12. Pensions and other post-retirement benefit obligations 30 September 2023 31 March 2023 £m £m Present value of funded obligations (17,502) (18,934) Fair value of plan assets 19,570 21,246 2,068 2,312 Present value of unfunded obligations (264) (292) Other post-employment liabilities (67) (69) Net defined benefit asset 1,737 1,951 Presented in consolidated statement of financial position: Assets 2,352 2,645 Liabilities (615) (694) 1,737 1,951 Key actuarial assumptions 30 September 2023 31 March 2023 Discount rate – UK past service 5.55 % 4.80 % Discount rate – US 5.70 % 4.85 % Rate of increase in RPI – UK past service 3.19 % 3.17 % The net pensions and other post-retirement benefit (OPEB) obligations position, as recorded under IAS 19, at 30 September 2023 was an asset of £1,737 million (31 March 2023: £1,951 million asset). The movement of £214 million primarily reflects asset performance being less than the discount rate at the start of the period, partially offset by increases in discount rates resulting in a decrease in liabilities. Net actuarial losses of £263 million have been reflected within the consolidated statement of comprehensive income. There was a loss of £1,754 million (UK £1,155 million; US £599 million) relating to asset performance which reflects returns on assets, both in the UK and US, being less than the discount rate at the beginning of the year. Changes in actuarial assumptions led to a gain on liabilities of £1,491 million (UK £793 million; US £698 million). This primarily reflected movements in discount rates which resulted from large increases in corporate bond yields. The pension and OPEB surpluses in both the UK and the US of £1,377 million and £975 million respectively (31 March 2023: £1,672 million and £973 million) continue to be recognised as assets under IFRIC 14 as explained on page 175 of the Annual Report and Accounts for the year ended 31 March 2023.

Commitments and contingencies

Commitments and contingencies	6 Months Ended
	Sep. 30, 2023
Subclassifications of assets, liabilities and equities [abstract]
Commitments and contingencies	13. Commitments and contingencies At 30 September 2023, there were commitments for future energy purchase agreements of £13,824 million (31 March 2023: £19,194 million) and future capital expenditure contracted but not provided for in relation to the acquisition of property, plant and equipment of £3,218 million (31 March 2023: £2,936 million). We also have contingencies in the form of certain guarantees and letters of credit. These are described in further detail in note 30 to the Annual Report and Accounts for the year ended 31 March 2023. Litigation and claims Through the ordinary course of our operations, we are party to various litigation, claims and investigations. We do not expect the ultimate resolution of any proceedings to have a material adverse effect on our results of operations, cash flows or financial position.

Exchange rates

Exchange rates	6 Months Ended
	Sep. 30, 2023
Foreign exchange rates [abstract]
Exchange rates	14. Exchange rates The consolidated results are affected by the exchange rates used to translate the results of our US operations and US dollar transactions. The US dollar to pound sterling exchange rates used were: 30 September 2023 2022 Year ended 31 March 2023 Closing rate applied at period end 1.22 1.12 1.23 Average rate applied for the period 1.25 1.21 1.22

Related party transactions

Related party transactions	6 Months Ended
	Sep. 30, 2023
Related party transactions [abstract]
Related party transactions	15. Related party transactionsRelated party transactions in the six months ended 30 September 2023 were substantially the same in nature to those disclosed in note 31 of the Annual Report and Accounts for the year ended 31 March 2023. There were no other related party transactions in the period that have materially affected the financial position or performance of the Group.

Additional disclosures in respe

Additional disclosures in respect of guaranteed securities	6 Months Ended
	Sep. 30, 2023
Separate Financial Statements [Abstract]
Additional disclosures in respect of guaranteed securities	16. Additional disclosures in respect of guaranteed securities Niagara Mohawk Power Corporation, a wholly owned subsidiary of the Group, has issued preferred shares that are listed on a US national securities exchange and are guaranteed by National Grid plc. This guarantor commits to honour any liabilities should the company issuing the debt have any financial difficulties. In order to provide debt holders with information on the financial stability of the company providing the guarantee, we are required to disclose individual financial information for this company. We have chosen to include this information in the half year financial information. The following summarised financial information is given in respect of Niagara Mohawk Power Corporation as a result of National Grid plc’s guarantee, dated 29 October 2007, of Niagara Mohawk Power Corporation’s 3.6% and 3.9% issued preferred shares, which amount to $23 million. National Grid plc’s guarantee of Niagara Mohawk Power Corporation’s preferred shares is full and unconditional. There are no restrictions on the payment of dividends by Niagara Mohawk Power Corporation or limitations on National Grid plc’s guarantee of the preferred shares, and there are no factors that may affect payments to holders of the guaranteed securities. The following summarised financial information for National Grid plc and Niagara Mohawk Power Corporation is presented on a combined basis and is intended to provide investors with meaningful and comparable financial information, and is provided pursuant to the early adoption of Rule 13-01 of Regulation S-X in lieu of the separate financial statements of Niagara Mohawk Power Corporation. Summarised financial information is presented, on a combined basis, as at 30 September 2023. The combined amounts are presented under IFRS measurement principles. Intercompany transactions between National Grid plc and Niagara Mohawk Power Corporation have been eliminated. Investments in other non-issuer and non-guarantor subsidiaries are included at cost, subject to impairment. National Grid plc and Niagara Mohawk Power Corporation combined Combined statement of financial position Non-current loans to other subsidiaries 126 Non-current assets 12,033 Current loans to other subsidiaries 15,557 Current assets 1,526 Current loans from other subsidiaries (6,893) Current liabilities (1,263) Non-current loans from other subsidiaries (2,080) Non-current liabilities (13,703) Net assets¹ 5,303 Equity 5,303 Combined income statement – continuing operations Revenue 1,594 Operating costs (1,330) Operating profit 264 Other income from other subsidiaries — Other income and costs, including taxation (51) Profit after tax 213 1. Excluded from net assets above are investments in other consolidated subsidiaries with a carrying value of £14,480 million.

Post balance sheet events

Post balance sheet events	6 Months Ended
	Sep. 30, 2023
Disclosure of non-adjusting events after reporting period [abstract]
Post balance sheet events	17. Post balance sheet events At the end of October 2023, legislation required to enable the separation of the ESO and formation of the ISOP was passed through Parliament. The ISOP is expected to be established as a Public Corporation in 2024, with responsibilities across both the electricity and gas systems. As a result, the Group took the judgement to classify the associated assets and liabilities of the ESO as held for sale in the consolidated statement of financial position at the end of October 2023 and the ESO will be measured at the lower of its carrying amount or fair value less costs to sell, which will take into consideration the current over-collection of allowed revenues .

Basis of preparation and new _2

Basis of preparation and new accounting standards, interpretations and amendments (Policies)	6 Months Ended
	Sep. 30, 2023
Accounting Policies, Changes In Accounting Estimates And Errors [Abstract]
Going concern	Going concern As part of the Directors’ consideration of the appropriateness of adopting the going concern basis of accounting in preparing the half year financial information, the Directors have considered the Group’s principal risks (discussed on page 60) alongside potential downside business cash flow scenarios impacting the Group’s operations. The Directors specifically considered both a base case and a reasonable worst-case scenario for business cash flows. The assessment is prepared on the conservative assumption that the Group has no access to the debt capital markets. The main additional cash flow impacts identified in the reasonable worst-case scenario are: • the timing of the sale of assets classified as held for sale; • adverse impacts of inflation and incremental spend on our capital expenditure programme; • adverse impact from timing across the Group (i.e. a net under-recovery of allowed revenues or reductions in over-collections) and slower collections of outstanding receivables; • higher operating and financing costs than expected; including non-delivery of planned efficiencies across the Group; and • the potential impact of further significant storm costs in the US. As part of their analysis, the Board also considered the following potential levers at their discretion to improve the position identified by the analysis if the debt capital markets are not accessible: • the payment of dividends to shareholders; • significant changes in the phasing of the Group’s capital expenditure programme, with elements of non-essential works and programmes delayed; and • a number of further reductions in operating expenditure across the Group. As at 30 September 2023, the Group had undrawn committed facilities available for general corporate purposes amounting to £8.0 billion. Based on these available liquidity resources and having considered the reasonable worst-case scenario, and the further levers at the Board’s discretion, the Group has not identified any material uncertainties relating to events or conditions that, individually or collectively, may cast significant doubt on its ability to continue as a going concern for the foreseeable future, a period not less than 12 months from the date of this report. In addition to the above, the ability to raise new and extend existing financing was separately included in the analysis, and the Directors noted the c.£3.0 billion of new long-term senior debt issued in the period from 1 April to 30 September 2023 as evidence of the Group’s ability to continue to have access to the debt capital markets if needed. Based on the above, the Directors have concluded the Group is well placed to manage its financing and other business risks satisfactorily, and have a reasonable expectation that the Group will have adequate resources to continue in operation for at least 12 months from the signing date of these consolidated interim financial statements. They therefore consider it appropriate to adopt the going concern basis of accounting in preparing the half year financial information.
New IFRS accounting standards, interpretations and amendments adopted in the period	New IFRS accounting standards, interpretations and amendments adopted in the periodThere are no new standards, interpretations or amendments, issued by the IASB or by the IFRS Interpretations Committee (IFRIC), that are applicable for the period commencing on 1 April 2023 and have had a material impact on the Group’s results.
New IFRS accounting standards, interpretations and amendments not yet adopted	New IFRS accounting standards, interpretations and amendments not yet adopted There are no new accounting standards and amendments to existing standards that have been issued, but are not yet effective that were not disclosed in our Annual Report and Accounts. The Group has not early adopted any standard, amendment or interpretation that has been issued but is not yet effective.
Segment analysis	Revenue and the results of the business are analysed by operating segment, based on the information the Board use internally for the purposes of evaluating the performance of each operating segment and determining resource allocation between them. The Board is National Grid’s chief operating decision maker (as defined by IFRS 8 ‘Operating Segments’) and assesses the profitability of a profit measure that excludes certain income and expenses. We call that measure ‘adjusted profit’. Adjusted profit excludes exceptional items and remeasurements (as defined in note 4) and is used by management to monitor financial performance as it is considered that it aids the comparability of our reported financial performance from year to year. As a matter of course, the Board also considers profitability by segment, excluding the effect of major storms and timing adjustments relating to revenue and certain pass-through costs. However, the measure of profit disclosed in this note is operating profit before exceptional items and remeasurements, as this is the measure that is most consistent with the IFRS results reported within these financial statements.
Revenue	Under IFRS 15 ‘Revenue from Contracts with Customers’, revenue is recorded as or when the Group satisfies a performance obligation by transferring a promised good or service to a customer. A good or service is transferred when the customer obtains control of that good or service. The transfer of control of our distribution or transmission services coincides with the use of our network, as electricity and gas pass through our network and reach our customers. The Group principally satisfies its performance obligations over time and the amount of revenue recorded corresponds to the amounts billed and accrued for volumes of gas and electricity delivered/transferred to/from our customers.
Exceptional items and remeasurements	To monitor our segmental financial performance, we use an adjusted consolidated profit measure that excludes certain income and expenses. We exclude items from adjusted profit because, if included, these items could distort understanding of our performance in the period and the comparability between periods. With respect to restructuring costs, these represent additional expenses incurred that are not related to normal business and day‑to-day activities. These can take place over multiple reporting periods given the scale of the Group, the nature and complexity of the transformation initiatives and due to the impact of strategic transactions. Remeasurements comprise unrealised gains or losses recorded in the consolidated income statement arising from changes in the fair value of certain financial assets and liabilities categorised as held at fair value through profit and loss (FVTPL). Once the fair value movements are realised (for example, when the derivative matures), the previously recognised fair value movements are then reversed through remeasurements and recognised within earnings before exceptional items and remeasurements. These assets and liabilities include commodity contracts and derivative financial instruments to the extent that hedge accounting is either not achieved or is not effective. We have also classified the unrealised gains or losses reported in profit and loss on certain additional assets treated as FVTPL within remeasurements. These relate to financial assets (which fail the ‘solely payments of principal and interest test’ under IFRS 9), the money market fund investments used by Group Treasury for cash management purposes and the net foreign exchange gains and losses on borrowing activities. These are offset by foreign exchange losses and gains on financing derivatives measured at fair value. In all cases, these fair values increase or decrease because of changes in foreign exchange, commodity or other financial indices over which we have no control.
Assets held for sale and discontinued operations	Assets and businesses are classified as held for sale when their carrying amounts are recovered through sale rather than through continuing use. They only meet the held for sale condition when the assets are ready for immediate sale in their present condition, management is committed to the sale and it is highly probable that the sale will complete within one year. Depreciation ceases on assets and businesses when they are classified as held for sale and the assets and businesses are impaired if their carrying value exceeds their fair value less expected costs to sell.The results and cash flows of assets or businesses classified as held for sale or sold during the year, that meet the criteria of being a major separate line of business or geographical area of operation, are shown separately from our continuing operations, and presented within discontinued operations in the income statement and cash flow statement.
Earnings per share	The earnings per share (EPS) calculations are based on profit after tax attributable to equity shareholders of the parent company which excludes non-controlling interests.
Guaranteed securities	Niagara Mohawk Power Corporation, a wholly owned subsidiary of the Group, has issued preferred shares that are listed on a US national securities exchange and are guaranteed by National Grid plc. This guarantor commits to honour any liabilities should the company issuing the debt have any financial difficulties. In order to provide debt holders with information on the financial stability of the company providing the guarantee, we are required to disclose individual financial information for this company. We have chosen to include this information in the half year financial information.

Segmental analysis (Tables)

Segmental analysis (Tables)	6 Months Ended
	Sep. 30, 2023
Disclosure of operating segments [abstract]
Schedule of information by operating segments	The following table describes the main activities for each reportable operating segment: UK Electricity Transmission The high-voltage electricity transmission networks in England and Wales. This includes our Accelerated Strategic Transmission Investment projects to connect more clean, low-carbon power to the transmission network in England and Wales. UK Electricity Distribution The electricity distribution networks of NGED in the East Midlands, West Midlands and South West of England and South Wales. UK Electricity System Operator The Great Britain system operator. The ESO has not met the criteria to be classified as held for sale as at 30 September 2023. New England Gas distribution networks, electricity distribution networks and high-voltage electricity transmission networks in New England. New York Gas distribution networks, electricity distribution networks and high-voltage electricity transmission networks in New York. National Grid Ventures Comprises all commercial operations in LNG at the Isle of Grain in the UK and Providence, Rhode Island in the US, our electricity generation business in the US, our electricity interconnectors in the UK and our investment in National Grid Renewables Development LLC, our renewables business in the US. NGV operates outside our regulated core business. Our US LNG operations were reclassified from the New England segment following an internal reorganisation in the period. Six months ended 30 September 2023 2022² Total sales Sales between segments 1 Sales to third parties Total sales Sales between segments 1 Sales to third £m £m £m £m £m £m Operating segments – continuing operations: UK Electricity Transmission 1,356 (19) 1,337 969 (14) 955 UK Electricity Distribution 850 (2) 848 1,005 (8) 997 UK Electricity System Operator 1,734 (17) 1,717 2,060 (15) 2,045 New England 1,441 — 1,441 1,760 — 1,760 New York 2,365 — 2,365 2,758 — 2,758 National Grid Ventures 666 (27) 639 685 (9) 676 Other 142 — 142 253 — 253 Total revenue from continuing operations 8,554 (65) 8,489 9,490 (46) 9,444 Geographical areas: UK 4,309 4,589 US 4,180 4,855 Total revenue from continuing operations 8,489 9,444 1. Sales between operating segments are priced having regard to the regulatory and legal requirements to which the businesses are subject. The analysis of revenue by geographical area is on the basis of destination. There are no material sales between the UK and US geographical areas. 2. Comparative amounts have been re-presented to reflect NGV as a separate operating segment. Before exceptional items and remeasurements Exceptional items and remeasurements (see note 4) After exceptional items and remeasurements Six months ended 30 September 2023 2022¹ 2023 2022¹ 2023 2022¹ £m £m £m £m £m £m Operating segments – continuing operations: UK Electricity Transmission 839 499 (1) (6) 838 493 UK Electricity Distribution 476 531 (4) (9) 472 522 UK Electricity System Operator 443 147 — (1) 443 146 New England (32) 193 (15) 527 (47) 720 New York (30) (18) 38 (8) 8 (26) National Grid Ventures 219 259 91 49 310 308 Other (13) 145 (26) (69) (39) 76 Total operating profit from continuing operations 1,902 1,756 83 483 1,985 2,239 Geographical areas: UK 1,956 1,550 60 (32) 2,016 1,518 US (54) 206 23 515 (31) 721 Total operating profit from continuing operations 1,902 1,756 83 483 1,985 2,239 1. Comparative amounts have been re-presented to reflect NGV as a separate operating segment. Before exceptional items and remeasurements Exceptional items and remeasurements (see note 4) After exceptional items and remeasurements Six months ended 30 September 2023 2022¹ 2023 2022¹ 2023 2022¹ £m £m £m £m £m £m Reconciliation to profit before tax: Operating profit from continuing operations 1,902 1,756 83 483 1,985 2,239 Share of post-tax results of joint ventures and associates 59 70 12 (19) 71 51 Finance income 123 69 (8) (32) 115 37 Finance costs (834) (801) 34 140 (800) (661) Total profit before tax from continuing operations 1,250 1,094 121 572 1,371 1,666 1. Comparative amounts have been re-presented to reflect the classification of the FAA option as held for sale and within discontinued operations. Capital expenditure represents additions to property, plant and equipment and other intangible assets but excludes additional investments in and loans to joint ventures and associates. Net book value of property, plant and equipment and other intangible assets Capital expenditure Depreciation, amortisation 30 September 2023 31 March 2023¹ 30 September 2023 30 September 2022¹ 30 September 2023 30 September 2022¹ £m £m £m £m £m £m Operating segments: UK Electricity Transmission 16,030 15,483 800 629 (250) (235) UK Electricity Distribution 13,940 13,462 608 584 (105) (104) UK Electricity System Operator 434 411 75 42 (52) (40) New England 13,781 13,033 789 801 (204) (184) New York 22,937 21,730 1,257 1,242 (321) (292) National Grid Ventures 3,956 3,880 175 410 (84) (73) Other 35 38 2 9 (5) (4) Total 71,113 68,037 3,706 3,717 (1,021) (932) Geographical areas: UK 33,475 32,343 1,649 1,594 (464) (432) US 37,638 35,694 2,057 2,123 (557) (500) Total 71,113 68,037 3,706 3,717 (1,021) (932) By asset type: Property, plant and equipment 67,396 64,433 3,449 3,490 (868) (829) Other intangible assets 3,717 3,604 257 227 (153) (103) Total 71,113 68,037 3,706 3,717 (1,021) (932) 1. Comparative amounts have been re-presented to reflect NGV as a separate operating segment and the reclassification of our US LNG operations from New England to NGV following an internal reorganisation in the period.

Revenue (Tables)

Revenue (Tables)	6 Months Ended
	Sep. 30, 2023
Revenue [abstract]
Schedule of disaggregation of revenue from contracts with customers	Revenue for the six months ended 30 September 2023 UK Electricity Transmission UK Electricity Distribution UK Electricity System Operator New New National Grid Ventures Other Total Revenue under IFRS 15 Transmission 1,299 — 5 43 283 426 — 2,056 Distribution — 810 — 1,329 2,047 — — 4,186 System Operator — — 1,712 — — — — 1,712 Other 1 9 36 — 4 7 75 — 131 Total IFRS 15 revenue 1,308 846 1,717 1,376 2,337 501 — 8,085 Other revenue Generation — — — — — 181 — 181 Other 2 29 2 — 65 28 (43) 142 223 Total other revenue 29 2 — 65 28 138 142 404 Total revenue from continuing operations 1,337 848 1,717 1,441 2,365 639 142 8,489 Geographic split of revenue for the six months ended 30 September 2023 UK Electricity Transmission UK Electricity Distribution UK Electricity System Operator New England New National Grid Ventures Other Total Revenue under IFRS 15 UK 1,308 846 1,717 — — 430 — 4,301 US — — — 1,376 2,337 71 — 3,784 Total IFRS 15 revenue 1,308 846 1,717 1,376 2,337 501 — 8,085 Other revenue UK 29 2 — — — (50) 27 8 US — — — 65 28 188 115 396 Total other revenue 29 2 — 65 28 138 142 404 Total revenue from continuing operations 1,337 848 1,717 1,441 2,365 639 142 8,489 1. The UK Electricity Transmission and UK Electricity Distribution other IFRS 15 revenue principally relates to engineering recharges, which are the recovery of costs incurred for construction work requested by customers, such as the re-routing of existing network assets. Within NGV, the other IFRS 15 revenue principally relates to revenue generated from our NG Renewables business. 2. Other revenue, recognised in accordance with accounting standards other than IFRS 15, includes property sales by our UK commercial property business, rental income, income arising in connection with the Transition Services Agreements in place following the sales of The Narragansett Electric Company (NECO) and the UK Gas Transmission business, and an adjustment to NGV revenue in respect of the interconnector cap and floor and Use of Revenue regimes constructed by Ofgem. Revenue for the six months ended 30 September 2022 UK Electricity Transmission UK Electricity Distribution UK Electricity System Operator New England New York National Grid Ventures¹ £m Other¹ £m Total Revenue under IFRS 15 Transmission 931 — 77 53 117 306 — 1,484 Distribution — 940 — 1,675 2,617 — — 5,232 System Operator — — 1,968 — — — — 1,968 Other 2 16 43 — 4 6 69 — 138 Total IFRS 15 revenue 947 983 2,045 1,732 2,740 375 — 8,822 Other revenue Generation — — — — — 224 — 224 Other 3 8 14 — 28 18 77 253 398 Total other revenue 8 14 — 28 18 301 253 622 Total revenue from continuing operations 955 997 2,045 1,760 2,758 676 253 9,444 Geographic split of revenue for the six months ended 30 September 2022 UK Electricity Transmission UK Electricity Distribution UK Electricity System Operator New England New York National Grid Ventures¹ £m Other¹ £m Total Revenue under IFRS 15 UK 947 983 2,045 — — 310 — 4,285 US — — — 1,732 2,740 65 — 4,537 Total IFRS 15 revenue 947 983 2,045 1,732 2,740 375 — 8,822 Other revenue UK 8 14 — — — 83 199 304 US — — — 28 18 218 54 318 Total other revenue 8 14 — 28 18 301 253 622 Total revenue from continuing operations 955 997 2,045 1,760 2,758 676 253 9,444 1. Comparative amounts have been re-presented to reflect NGV as a separate operating segment. 2. The UK Electricity Transmission and UK Electricity Distribution other IFRS 15 revenue principally relates to engineering recharges, which are the recovery of costs incurred for construction work requested by customers, such as the re-routing of existing network assets. Within NGV, the other IFRS 15 revenue principally relates to revenue generated from our NG Renewables business.

Exceptional items and remeasu_2

Exceptional items and remeasurements (Tables)	6 Months Ended
	Sep. 30, 2023
Exceptional Items And Remeasurements [Abstract]
Schedule of exceptional items and remeasurements from continuing operations	Six months ended 30 September 2023 Exceptional items Remeasurements Total Included within operating profit from continuing operations Cost efficiency programme (39) — (39) Transaction, separation and integration costs¹ (11) — (11) IFA1 fire insurance proceeds 92 — 92 Net gains on commodity contract derivatives — 41 41 42 41 83 Six months ended 30 September 2022² Exceptional items Remeasurements Total Included within operating profit from continuing operations Net gain on disposal of NECO 511 — 511 Cost efficiency programme (61) — (61) Transaction, separation and integration costs 1 (65) — (65) IFA1 fire insurance proceeds 33 — 33 Net gains on commodity contract derivatives — 65 65 418 65 483 1. Transaction, separation and integration costs represent the aggregate of distinct activities undertaken by the Group in the periods presented. 2. Comparative amounts have been re-presented to reflect the classification of the FAA option as held for sale and within discontinued operations. Details of remeasurements, tax exceptional items and the tax effect of exceptional items and remeasurements are also provided in this note. Six months ended 30 September 2023 Exceptional items Remeasurements Total Included within operating profit from continuing operations 42 41 83 Included within net finance costs (note 5) Net gains on derivative financial instruments — 34 34 Net losses on financial assets at fair value through profit and loss — (8) (8) — 26 26 Included within share of post-tax results of joint ventures and associates Net gains on financial instruments — 12 12 — 12 12 Total included within profit before tax from continuing operations 42 79 121 Tax on exceptional items and remeasurements 1 (21) (20) Total exceptional items and remeasurements after tax from 43 58 101 Six months ended 30 September 2022¹ Exceptional items Remeasurements Total Included within operating profit from continuing operations 418 65 483 Included within net finance costs (note 5) Net gains on derivative financial instruments — 140 140 Net losses on financial assets at fair value through profit and loss — (32) (32) — 108 108 Included within share of post-tax results of joint ventures and associates Net losses on financial instruments — (19) (19) — (19) (19) Total included within profit before tax from continuing operations 418 154 572 Tax on exceptional items and remeasurements (221) (49) (270) Total exceptional items and remeasurements after tax from 197 105 302 1. Comparative amounts have been re-presented to reflect the classification of the FAA option as held for sale and within discontinued operations.

Finance income and costs (Table

Finance income and costs (Tables)	6 Months Ended
	Sep. 30, 2023
Analysis of income and expense [abstract]
Schedule of finance income and costs	2023 2022¹ Six months ended 30 September Notes £m £m Finance income Interest income from financing activities 52 14 Net interest on pensions and other post-retirement benefit obligations 51 41 Net losses on financial assets at fair value through profit and loss (8) (32) Other interest income 20 14 115 37 Finance costs Interest expense on financial instruments 2 (903) (878) Unwinding of discount on provisions (50) (42) Other interest (8) 8 Net gains on derivative financial instruments 3 34 140 Less: interest capitalised 4 127 111 (800) (661) Net finance costs (685) (624) 1. Comparative amounts have been re-presented to reflect the classification of the FAA option as held for sale and within discontinued operations. 2. Finance costs include principal accretion on inflation-linked debt of £149 million (2022: £240 million) and income related to principal accretion on inflation-linked swaps of £18 million (2022: £5 million expense). 3. Includes a net foreign exchange gain on borrowing activities, offset by foreign exchange losses and gains on financing derivatives measured at fair value.

Assets held for sale and disc_2

Assets held for sale and discontinued operations (Tables)	6 Months Ended
	Sep. 30, 2023
Non-current assets or disposal groups classified as held for sale or as held for distribution to owners [abstract]
Schedule of assets and liabilities classified as held for sale	The following assets and liabilities were classified as held for sale: 30 September 2023 31 March 2023 Total assets Total liabilities held for sale Net assets held for sale Total assets Total liabilities held for sale Net assets held for sale Investment in GasT TopCo Limited 1,441 — 1,441 1,443 — 1,443 FAA option — — — — (109) (109) FAA forward — (7) (7) — — — RAA option — (44) (44) — — — Net assets held for sale 1,441 (51) 1,390 1,443 (109) 1,334
Summary of discontinued operations	The summary income statements for the periods ended 30 September 2023 and 2022 are as follows: 2023 2022¹ £m £m Discontinued operations Revenue — 805 Other operating costs — (459) Operating profit — 346 Finance income 9 9 Finance costs² 61 (261) Profit/(loss) before tax 70 94 Tax (5) (57) Profit/(loss) after tax from discontinued operations 65 37 1. Comparative amounts have been re-presented to reflect the classification of the FAA option as held for sale and within discontinued operations. 2. Finance costs include the remeasurement of the FAA option, the FAA forward and the RAA option. The summary statements of comprehensive income are as follows: 2023 2022¹ £m £m Profit after tax from discontinued operations 65 37 Other comprehensive (loss)/income from discontinued operations Items from discontinued operations that will never be reclassified to profit or loss: Remeasurement losses on pension assets and post-retirement benefit obligations — (126) Tax on items that will never be reclassified to profit or loss — 31 Total losses from discontinued operations that will never be reclassified to profit or loss — (95) Items from discontinued operations that may be reclassified subsequently to profit or loss: Net gains in respect of cash flow hedges — 8 Net gains in respect of cost of hedging — 4 Net losses on investments in debt instruments measured at fair value through other (12) — Tax on items that may be reclassified subsequently to profit or loss 3 (3) Total (losses)/gains from discontinued operations that may be reclassified subsequently to profit or loss (9) 9 Other comprehensive loss for the period, net of tax, from discontinued operations (9) (86) Total comprehensive income/(loss) for the period from discontinued operations 56 (49) 1. Comparative amounts have been re-presented to reflect the classification of the FAA option as held for sale and within discontinued operations.

Earnings per share (Tables)

Earnings per share (Tables)	6 Months Ended
	Sep. 30, 2023
Earnings per share [abstract]
Schedule of basic and diluted earnings per share	Basic earnings per share Earnings EPS Earnings EPS Six months ended 30 September 2023 2023 2022¹ 2022¹ £m pence £m pence Profit after tax from continuing operations attributable to the parent 1,063 28.8 1,219 33.4 Profit after tax from discontinued operations attributable to the parent 65 1.8 37 1 Total profit after tax attributable to the parent 1,128 30.6 1,256 34.4 2023 2022 millions millions Weighted average number of shares – basic 3,682 3,651 1. Comparative amounts have been re-presented to reflect the classification of the FAA option as held for sale and within discontinued operations. (b) Diluted earnings per share Earnings EPS Earnings EPS Six months ended 30 September 2023 2023 2022¹ 2022¹ £m pence £m pence Profit after tax from continuing operations attributable to the parent 1,063 28.7 1,219 33.2 Profit after tax from discontinued operations attributable to the parent 65 1.8 37 1 Total profit after tax attributable to the parent 1,128 30.5 1,256 34.2 2023 2022 millions millions Weighted average number of shares – diluted 3,700 3,668 1. Comparative amounts have been re-presented to reflect the classification of the FAA option as held for sale and within discontinued operations.

Dividends (Tables)

Dividends (Tables)	6 Months Ended
	Sep. 30, 2023
Subclassifications of assets, liabilities and equities [abstract]
Schedule of dividends	Pence Cash Scrip Ordinary dividends Final dividend in respect of the year ended 31 March 2023 37.60 1,325 56 Interim dividend in respect of the year ended 31 March 2023 17.84 488 163 Final dividend in respect of the year ended 31 March 2022 33.76 1,119 114

Fair value measurement (Tables)

Fair value measurement (Tables)	6 Months Ended
	Sep. 30, 2023
Fair Value Measurement [Abstract]
Schedule of fair value measurement of assets	The following table categorises these assets and liabilities by the valuation methodology applied in determining their fair value using the fair value hierarchy described on page 197 of the Annual Report and Accounts for the year ended 31 March 2023. 30 September 2023 31 March 2023 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Investments held at fair value through profit and loss 1,007 — 483 1,490 1,764 — 452 2,216 Investments held at fair value through other comprehensive income 1 — 388 — 388 — 407 — 407 Financing derivatives — 309 20 329 — 341 22 363 Commodity contract derivatives — 54 2 56 — 62 4 66 1,007 751 505 2,263 1,764 810 478 3,052 Liabilities Financing derivatives — (1,219) (95) (1,314) — (997) (122) (1,119) Commodity contract derivatives — (78) (45) (123) — (134) (40) (174) Contingent consideration 2 — — (10) (10) — — (19) (19) — (1,297) (150) (1,447) — (1,131) (181) (1,312) Total 1,007 (546) 355 816 1,764 (321) 297 1,740 1. Investments held include instruments which meet the criteria of IFRS 9 or IAS 19. 2. Contingent consideration relates to the acquisition of National Grid Renewables Development LLC. The changes in fair value of our level 3 financial assets and liabilities in the six months to 30 September are presented below: Financing derivatives Commodity contract derivatives Other 1 Total 2023 2022 2023 2022 2023 2022 2023 2022 £m £m £m £m £m £m £m £m At 1 April (100) (187) (36) 44 433 376 297 233 Net gains/(losses) through the consolidated income statement for the period 2,3 25 76 (4) 44 26 30 47 150 Purchases — (133) (10) (56) 11 37 1 (152) Settlements — — 7 (4) 3 (4) 10 (8) At 30 September 4 (75) (244) (43) 28 473 439 355 223 1. Other comprises our investments in Sunrun Neptune 2016 LLC and the investments made by National Grid Partners, which are accounted for at fair value through profit and loss and the contingent consideration arising from the acquisition of National Grid Renewables Development LLC. Net gains and loss are recognised within finance income and costs in the income statement. 2. Gains of £25 million (2022: gains of £93 million) are attributable to derivative financial instruments held at the end of the reporting period and have been recognised in finance costs in the income statement. 3. Losses of £15 million (2022: losses of £23 million) are attributable to the commodity contract derivative financial instruments held at the end of the reporting period and have been recognised in other operating costs in the consolidated income statement. 4. There were no reclassifications in or out of level 3 (2022: none).
Schedule of fair value measurement of liabilities	The following table categorises these assets and liabilities by the valuation methodology applied in determining their fair value using the fair value hierarchy described on page 197 of the Annual Report and Accounts for the year ended 31 March 2023. 30 September 2023 31 March 2023 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Investments held at fair value through profit and loss 1,007 — 483 1,490 1,764 — 452 2,216 Investments held at fair value through other comprehensive income 1 — 388 — 388 — 407 — 407 Financing derivatives — 309 20 329 — 341 22 363 Commodity contract derivatives — 54 2 56 — 62 4 66 1,007 751 505 2,263 1,764 810 478 3,052 Liabilities Financing derivatives — (1,219) (95) (1,314) — (997) (122) (1,119) Commodity contract derivatives — (78) (45) (123) — (134) (40) (174) Contingent consideration 2 — — (10) (10) — — (19) (19) — (1,297) (150) (1,447) — (1,131) (181) (1,312) Total 1,007 (546) 355 816 1,764 (321) 297 1,740 1. Investments held include instruments which meet the criteria of IFRS 9 or IAS 19. 2. Contingent consideration relates to the acquisition of National Grid Renewables Development LLC. The changes in fair value of our level 3 financial assets and liabilities in the six months to 30 September are presented below: Financing derivatives Commodity contract derivatives Other 1 Total 2023 2022 2023 2022 2023 2022 2023 2022 £m £m £m £m £m £m £m £m At 1 April (100) (187) (36) 44 433 376 297 233 Net gains/(losses) through the consolidated income statement for the period 2,3 25 76 (4) 44 26 30 47 150 Purchases — (133) (10) (56) 11 37 1 (152) Settlements — — 7 (4) 3 (4) 10 (8) At 30 September 4 (75) (244) (43) 28 473 439 355 223 1. Other comprises our investments in Sunrun Neptune 2016 LLC and the investments made by National Grid Partners, which are accounted for at fair value through profit and loss and the contingent consideration arising from the acquisition of National Grid Renewables Development LLC. Net gains and loss are recognised within finance income and costs in the income statement. 2. Gains of £25 million (2022: gains of £93 million) are attributable to derivative financial instruments held at the end of the reporting period and have been recognised in finance costs in the income statement. 3. Losses of £15 million (2022: losses of £23 million) are attributable to the commodity contract derivative financial instruments held at the end of the reporting period and have been recognised in other operating costs in the consolidated income statement. 4. There were no reclassifications in or out of level 3 (2022: none).
Schedule of impacts of reasonably possible changes in significant Level 3 assumptions	The impacts on a post-tax basis of reasonably possible changes in significant assumptions used in valuing assets and liabilities classified within level 3 of the fair value hierarchy are as follows: Financing derivatives Commodity contract derivatives Other Six months ended 30 September 2023 2022 2023 2022 2023 2022 £m £m £m £m £m £m 10% increase in commodity prices — — 15 35 — — 10% decrease in commodity prices — — (15) (36) — — +10% market area price change — — 12 7 — — -10% market area price change — — (11) (7) — — +20 basis point increase in Limited Price Index (38) (51) — — — — -20 basis point decrease in LPI market curve 38 51 — — — — +20 basis point increase between Retail Price Index (RPI) and Consumer Price Index (CPI) 36 17 — — — — -20 basis point decrease between RPI and CPI market curves (33) (16) — — — — +50 basis points change in discount rate — — — — (8) (9) -50 basis points change in discount rate — — — — 9 10 +10% change in venture capital price — — — — 30 — -10% change in venture capital price — — — — (30) —

Net debt (Tables)

Net debt (Tables)	6 Months Ended
	Sep. 30, 2023
Subclassifications of assets, liabilities and equities [abstract]
Schedule of components of net debt	Net debt is comprised as follows: 30 September 2023 31 March 2023 £m £m Cash and cash equivalents 227 163 Current financial investments 1,680 2,605 Borrowings and bank overdrafts (44,797) (42,985) Financing derivatives 1 (985) (756) Net debt (net of related derivative financial instruments) (43,875) (40,973) 1. Includes £4 million liability (31 March 2023: £4 million liability) in relation to the hedging of capital expenditure. The cash flows related to these derivatives are included within investing activities in the consolidated cash flow statement which is in the same manner as the transactions which are the subject of the hedges. The financing derivatives balance included in net debt exclude the commodity derivatives.
Schedule of balance sheet allocation of derivative balances	The following table splits out the total derivative balances on the face of the consolidated statement of financial position by category: 30 September 2023 31 March 2023 Assets Liabilities Total Assets Liabilities Total Financing derivatives 329 (1,314) (985) 363 (1,119) (756) Commodity contract derivatives 56 (123) (67) 66 (174) (108) Total derivative financial instruments 385 (1,437) (1,052) 429 (1,293) (864)

Pensions and other post-retir_2

Pensions and other post-retirement benefit obligations (Tables)	6 Months Ended
	Sep. 30, 2023
Employee Benefits [Abstract]
Schedule of defined benefit plan recognised in balance sheet	30 September 2023 31 March 2023 £m £m Present value of funded obligations (17,502) (18,934) Fair value of plan assets 19,570 21,246 2,068 2,312 Present value of unfunded obligations (264) (292) Other post-employment liabilities (67) (69) Net defined benefit asset 1,737 1,951 Presented in consolidated statement of financial position: Assets 2,352 2,645 Liabilities (615) (694) 1,737 1,951
Schedule of key actuarial assumptions	Key actuarial assumptions 30 September 2023 31 March 2023 Discount rate – UK past service 5.55 % 4.80 % Discount rate – US 5.70 % 4.85 % Rate of increase in RPI – UK past service 3.19 % 3.17 %

Exchange rates (Tables)

Exchange rates (Tables)	6 Months Ended
	Sep. 30, 2023
Foreign exchange rates [abstract]
Schedule of average and closing foreign exchange rates	The US dollar to pound sterling exchange rates used were: 30 September 2023 2022 Year ended 31 March 2023 Closing rate applied at period end 1.22 1.12 1.23 Average rate applied for the period 1.25 1.21 1.22

Additional disclosures in res_2

Additional disclosures in respect of guaranteed securities (Tables)	6 Months Ended
	Sep. 30, 2023
Seperate Financial Statements [Abstract]
Disclosure of Combined Statement of Financial Position	National Grid plc and Niagara Mohawk Power Corporation combined Combined statement of financial position Non-current loans to other subsidiaries 126 Non-current assets 12,033 Current loans to other subsidiaries 15,557 Current assets 1,526 Current loans from other subsidiaries (6,893) Current liabilities (1,263) Non-current loans from other subsidiaries (2,080) Non-current liabilities (13,703) Net assets¹ 5,303 Equity 5,303 Combined income statement – continuing operations Revenue 1,594 Operating costs (1,330) Operating profit 264 Other income from other subsidiaries — Other income and costs, including taxation (51) Profit after tax 213 1. Excluded from net assets above are investments in other consolidated subsidiaries with a carrying value of £14,480 million.
Disclosure of Combined Income Statement	National Grid plc and Niagara Mohawk Power Corporation combined Combined statement of financial position Non-current loans to other subsidiaries 126 Non-current assets 12,033 Current loans to other subsidiaries 15,557 Current assets 1,526 Current loans from other subsidiaries (6,893) Current liabilities (1,263) Non-current loans from other subsidiaries (2,080) Non-current liabilities (13,703) Net assets¹ 5,303 Equity 5,303 Combined income statement – continuing operations Revenue 1,594 Operating costs (1,330) Operating profit 264 Other income from other subsidiaries — Other income and costs, including taxation (51) Profit after tax 213 1. Excluded from net assets above are investments in other consolidated subsidiaries with a carrying value of £14,480 million.

Basis of preparation and new _3

Basis of preparation and new accounting standards, interpretations and amendments (Details) - GBP (£) £ in Billions	Jul. 19, 2023	Mar. 31, 2023	Jan. 31, 2023	Sep. 30, 2023
Disclosure of detailed information about borrowings [line items]
Undrawn borrowing facilities				£ 8
GasT TopCo Limited
Disclosure of detailed information about borrowings [line items]
Proportion of ownership interest in associate	20%	40%	40%
Fixed interest rate bonds
Disclosure of detailed information about borrowings [line items]
Notional amount				£ 3

Segmental analysis - Narrative

Segmental analysis - Narrative (Details)	Sep. 30, 2023 segment
Disclosure of operating segments [abstract]
Number of reportable operating segments	6

Segmental analysis - Schedule o

Segmental analysis - Schedule of revenue by segment (Details) - GBP (£) £ in Millions	6 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Disclosure of operating segments [line items]
Total revenue from continuing operations	£ 8,489	£ 9,444	[1]
UK
Disclosure of operating segments [line items]
Total revenue from continuing operations	4,309	4,589
US
Disclosure of operating segments [line items]
Total revenue from continuing operations	4,180	4,855
UK Electricity Transmission
Disclosure of operating segments [line items]
Total revenue from continuing operations	1,337	955
UK Electricity Distribution
Disclosure of operating segments [line items]
Total revenue from continuing operations	848	997
UK Electricity System Operator
Disclosure of operating segments [line items]
Total revenue from continuing operations	1,717	2,045
New England
Disclosure of operating segments [line items]
Total revenue from continuing operations	1,441	1,760
New York
Disclosure of operating segments [line items]
Total revenue from continuing operations	2,365	2,758
National Grid Ventures
Disclosure of operating segments [line items]
Total revenue from continuing operations	639	676
Other
Disclosure of operating segments [line items]
Total revenue from continuing operations	142	253
Operating segments
Disclosure of operating segments [line items]
Total revenue from continuing operations	8,554	9,490
Operating segments | UK Electricity Transmission
Disclosure of operating segments [line items]
Total revenue from continuing operations	1,356	969
Operating segments | UK Electricity Distribution
Disclosure of operating segments [line items]
Total revenue from continuing operations	850	1,005
Operating segments | UK Electricity System Operator
Disclosure of operating segments [line items]
Total revenue from continuing operations	1,734	2,060
Operating segments | New England
Disclosure of operating segments [line items]
Total revenue from continuing operations	1,441	1,760
Operating segments | New York
Disclosure of operating segments [line items]
Total revenue from continuing operations	2,365	2,758
Operating segments | National Grid Ventures
Disclosure of operating segments [line items]
Total revenue from continuing operations	666	685
Operating segments | Other
Disclosure of operating segments [line items]
Total revenue from continuing operations	142	253
Sales between segments
Disclosure of operating segments [line items]
Total revenue from continuing operations	(65)	(46)
Sales between segments | UK Electricity Transmission
Disclosure of operating segments [line items]
Total revenue from continuing operations	(19)	(14)
Sales between segments | UK Electricity Distribution
Disclosure of operating segments [line items]
Total revenue from continuing operations	(2)	(8)
Sales between segments | UK Electricity System Operator
Disclosure of operating segments [line items]
Total revenue from continuing operations	(17)	(15)
Sales between segments | New England
Disclosure of operating segments [line items]
Total revenue from continuing operations	0	0
Sales between segments | New York
Disclosure of operating segments [line items]
Total revenue from continuing operations	0	0
Sales between segments | National Grid Ventures
Disclosure of operating segments [line items]
Total revenue from continuing operations	(27)	(9)
Sales between segments | Other
Disclosure of operating segments [line items]
Total revenue from continuing operations	£ 0	£ 0
[1]Comparative amounts have been re-presented to reflect the classification of the Further Acquisition Agreement (the FAA option) as held for sale and within discontinued operations.

Segmental analysis - Schedule_2

Segmental analysis - Schedule of operating profit/(loss) by segment (Details) - GBP (£) £ in Millions	6 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Disclosure of operating segments [line items]
Operating profit from continuing operations	£ 1,985	£ 2,239	[1]
Share of post-tax results of joint ventures and associates	71	51	[1]
Finance income	115	37	[1]
Finance costs	(800)	(661)	[1]
Profit before tax	1,371	1,666	[1]
UK
Disclosure of operating segments [line items]
Operating profit from continuing operations	2,016	1,518
US
Disclosure of operating segments [line items]
Operating profit from continuing operations	(31)	721
Operating segments | UK Electricity Transmission
Disclosure of operating segments [line items]
Operating profit from continuing operations	838	493
Operating segments | UK Electricity Distribution
Disclosure of operating segments [line items]
Operating profit from continuing operations	472	522
Operating segments | UK Electricity System Operator
Disclosure of operating segments [line items]
Operating profit from continuing operations	443	146
Operating segments | New England
Disclosure of operating segments [line items]
Operating profit from continuing operations	(47)	720
Operating segments | New York
Disclosure of operating segments [line items]
Operating profit from continuing operations	8	(26)
Operating segments | National Grid Ventures
Disclosure of operating segments [line items]
Operating profit from continuing operations	310	308
Operating segments | Other
Disclosure of operating segments [line items]
Operating profit from continuing operations	(39)	76
Before exceptional items and remeasurements
Disclosure of operating segments [line items]
Operating profit from continuing operations	1,902	1,756
Share of post-tax results of joint ventures and associates	59	70
Finance income	123	69
Finance costs	(834)	(801)
Profit before tax	1,250	1,094
Before exceptional items and remeasurements | UK
Disclosure of operating segments [line items]
Operating profit from continuing operations	1,956	1,550
Before exceptional items and remeasurements | US
Disclosure of operating segments [line items]
Operating profit from continuing operations	(54)	206
Before exceptional items and remeasurements | Operating segments | UK Electricity Transmission
Disclosure of operating segments [line items]
Operating profit from continuing operations	839	499
Before exceptional items and remeasurements | Operating segments | UK Electricity Distribution
Disclosure of operating segments [line items]
Operating profit from continuing operations	476	531
Before exceptional items and remeasurements | Operating segments | UK Electricity System Operator
Disclosure of operating segments [line items]
Operating profit from continuing operations	443	147
Before exceptional items and remeasurements | Operating segments | New England
Disclosure of operating segments [line items]
Operating profit from continuing operations	(32)	193
Before exceptional items and remeasurements | Operating segments | New York
Disclosure of operating segments [line items]
Operating profit from continuing operations	(30)	(18)
Before exceptional items and remeasurements | Operating segments | National Grid Ventures
Disclosure of operating segments [line items]
Operating profit from continuing operations	219	259
Before exceptional items and remeasurements | Operating segments | Other
Disclosure of operating segments [line items]
Operating profit from continuing operations	(13)	145
Exceptional items and remeasurements (see note 4)
Disclosure of operating segments [line items]
Operating profit from continuing operations	83	483
Share of post-tax results of joint ventures and associates	12	(19)
Finance income	(8)	(32)
Finance costs	34	140
Profit before tax	121	572
Exceptional items and remeasurements (see note 4) | UK
Disclosure of operating segments [line items]
Operating profit from continuing operations	60	(32)
Exceptional items and remeasurements (see note 4) | US
Disclosure of operating segments [line items]
Operating profit from continuing operations	23	515
Exceptional items and remeasurements (see note 4) | Operating segments | UK Electricity Transmission
Disclosure of operating segments [line items]
Operating profit from continuing operations	(1)	(6)
Exceptional items and remeasurements (see note 4) | Operating segments | UK Electricity Distribution
Disclosure of operating segments [line items]
Operating profit from continuing operations	(4)	(9)
Exceptional items and remeasurements (see note 4) | Operating segments | UK Electricity System Operator
Disclosure of operating segments [line items]
Operating profit from continuing operations	0	(1)
Exceptional items and remeasurements (see note 4) | Operating segments | New England
Disclosure of operating segments [line items]
Operating profit from continuing operations	(15)	527
Exceptional items and remeasurements (see note 4) | Operating segments | New York
Disclosure of operating segments [line items]
Operating profit from continuing operations	38	(8)
Exceptional items and remeasurements (see note 4) | Operating segments | National Grid Ventures
Disclosure of operating segments [line items]
Operating profit from continuing operations	91	49
Exceptional items and remeasurements (see note 4) | Operating segments | Other
Disclosure of operating segments [line items]
Operating profit from continuing operations	£ (26)	£ (69)
[1]Comparative amounts have been re-presented to reflect the classification of the Further Acquisition Agreement (the FAA option) as held for sale and within discontinued operations.

Segmental analysis - Schedule_3

Segmental analysis - Schedule of capital expenditure by segment (Details) - GBP (£) £ in Millions	6 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Mar. 31, 2023
Disclosure of operating segments [line items]
Net book value of property, plant and equipment and other intangible assets	£ 71,113		£ 68,037
Capital expenditure	3,706	£ 3,717
Depreciation, amortisation and impairment	(1,021)	(932)
Operating segments | UK Electricity Transmission
Disclosure of operating segments [line items]
Net book value of property, plant and equipment and other intangible assets	16,030		15,483
Capital expenditure	800	629
Depreciation, amortisation and impairment	(250)	(235)
Operating segments | UK Electricity Distribution
Disclosure of operating segments [line items]
Net book value of property, plant and equipment and other intangible assets	13,940		13,462
Capital expenditure	608	584
Depreciation, amortisation and impairment	(105)	(104)
Operating segments | UK Electricity System Operator
Disclosure of operating segments [line items]
Net book value of property, plant and equipment and other intangible assets	434		411
Capital expenditure	75	42
Depreciation, amortisation and impairment	(52)	(40)
Operating segments | New England
Disclosure of operating segments [line items]
Net book value of property, plant and equipment and other intangible assets	13,781		13,033
Capital expenditure	789	801
Depreciation, amortisation and impairment	(204)	(184)
Operating segments | New York
Disclosure of operating segments [line items]
Net book value of property, plant and equipment and other intangible assets	22,937		21,730
Capital expenditure	1,257	1,242
Depreciation, amortisation and impairment	(321)	(292)
Operating segments | National Grid Ventures
Disclosure of operating segments [line items]
Net book value of property, plant and equipment and other intangible assets	3,956		3,880
Capital expenditure	175	410
Depreciation, amortisation and impairment	(84)	(73)
Operating segments | Other
Disclosure of operating segments [line items]
Net book value of property, plant and equipment and other intangible assets	35		38
Capital expenditure	2	9
Depreciation, amortisation and impairment	(5)	(4)
UK
Disclosure of operating segments [line items]
Net book value of property, plant and equipment and other intangible assets	33,475		32,343
Capital expenditure	1,649	1,594
Depreciation, amortisation and impairment	(464)	(432)
US
Disclosure of operating segments [line items]
Net book value of property, plant and equipment and other intangible assets	37,638		35,694
Capital expenditure	2,057	2,123
Depreciation, amortisation and impairment	(557)	(500)
Property, plant and equipment
Disclosure of operating segments [line items]
Net book value of property, plant and equipment and other intangible assets	67,396		64,433
Capital expenditure	3,449	3,490
Depreciation, amortisation and impairment	(868)	(829)
Other intangible assets
Disclosure of operating segments [line items]
Net book value of property, plant and equipment and other intangible assets	3,717		£ 3,604
Capital expenditure	257	227
Depreciation, amortisation and impairment	£ (153)	£ (103)

Revenue (Details)

Revenue (Details) - GBP (£) £ in Millions	6 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	£ 8,085	£ 8,822
Total other revenue	404	622
Total revenue from continuing operations	8,489	9,444	[1]
UK
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	4,301	4,285
Total other revenue	8	304
Total revenue from continuing operations	4,309	4,589
US
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	3,784	4,537
Total other revenue	396	318
Total revenue from continuing operations	4,180	4,855
UK Electricity Transmission
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	1,308	947
Total other revenue	29	8
Total revenue from continuing operations	1,337	955
UK Electricity Transmission | UK
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	1,308	947
Total other revenue	29	8
UK Electricity Transmission | US
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	0	0
Total other revenue	0	0
UK Electricity Distribution
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	846	983
Total other revenue	2	14
Total revenue from continuing operations	848	997
UK Electricity Distribution | UK
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	846	983
Total other revenue	2	14
UK Electricity Distribution | US
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	0	0
Total other revenue	0	0
UK Electricity System Operator
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	1,717	2,045
Total other revenue	0	0
Total revenue from continuing operations	1,717	2,045
UK Electricity System Operator | UK
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	1,717	2,045
Total other revenue	0	0
UK Electricity System Operator | US
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	0	0
Total other revenue	0	0
New England
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	1,376	1,732
Total other revenue	65	28
Total revenue from continuing operations	1,441	1,760
New England | UK
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	0	0
Total other revenue	0	0
New England | US
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	1,376	1,732
Total other revenue	65	28
New York
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	2,337	2,740
Total other revenue	28	18
Total revenue from continuing operations	2,365	2,758
New York | UK
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	0	0
Total other revenue	0	0
New York | US
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	2,337	2,740
Total other revenue	28	18
National Grid Ventures
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	501	375
Total other revenue	138	301
Total revenue from continuing operations	639	676
National Grid Ventures | UK
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	430	310
Total other revenue	(50)	83
National Grid Ventures | US
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	71	65
Total other revenue	188	218
Other
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	0	0
Total other revenue	142	253
Total revenue from continuing operations	142	253
Other | UK
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	0	0
Total other revenue	27	199
Other | US
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	0	0
Total other revenue	115	54
Transmission
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	2,056	1,484
Transmission | UK Electricity Transmission
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	1,299	931
Transmission | UK Electricity Distribution
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	0	0
Transmission | UK Electricity System Operator
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	5	77
Transmission | New England
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	43	53
Transmission | New York
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	283	117
Transmission | National Grid Ventures
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	426	306
Transmission | Other
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	0	0
Distribution
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	4,186	5,232
Distribution | UK Electricity Transmission
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	0	0
Distribution | UK Electricity Distribution
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	810	940
Distribution | UK Electricity System Operator
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	0	0
Distribution | New England
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	1,329	1,675
Distribution | New York
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	2,047	2,617
Distribution | National Grid Ventures
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	0	0
Distribution | Other
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	0	0
System Operator
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	1,712	1,968
System Operator | UK Electricity Transmission
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	0	0
System Operator | UK Electricity Distribution
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	0	0
System Operator | UK Electricity System Operator
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	1,712	1,968
System Operator | New England
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	0	0
System Operator | New York
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	0	0
System Operator | National Grid Ventures
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	0	0
System Operator | Other
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	0	0
Generation
Revenue from Contracts with Customers [line items]
Total other revenue	181	224
Generation | UK Electricity Transmission
Revenue from Contracts with Customers [line items]
Total other revenue	0	0
Generation | UK Electricity Distribution
Revenue from Contracts with Customers [line items]
Total other revenue	0	0
Generation | UK Electricity System Operator
Revenue from Contracts with Customers [line items]
Total other revenue	0	0
Generation | New England
Revenue from Contracts with Customers [line items]
Total other revenue	0	0
Generation | New York
Revenue from Contracts with Customers [line items]
Total other revenue	0	0
Generation | National Grid Ventures
Revenue from Contracts with Customers [line items]
Total other revenue	181	224
Generation | Other
Revenue from Contracts with Customers [line items]
Total other revenue	0	0
Other
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	131	138
Total other revenue	223	398
Other | UK Electricity Transmission
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	9	16
Total other revenue	29	8
Other | UK Electricity Distribution
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	36	43
Total other revenue	2	14
Other | UK Electricity System Operator
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	0	0
Total other revenue	0	0
Other | New England
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	4	4
Total other revenue	65	28
Other | New York
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	7	6
Total other revenue	28	18
Other | National Grid Ventures
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	75	69
Total other revenue	(43)	77
Other | Other
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	0	0
Total other revenue	£ 142	£ 253
[1]Comparative amounts have been re-presented to reflect the classification of the Further Acquisition Agreement (the FAA option) as held for sale and within discontinued operations.

Exceptional items and remeasu_3

Exceptional items and remeasurements - Schedule of exceptional items and remeasurements from continuing operations (Details) - GBP (£) £ in Millions	6 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Included within operating profit from continuing operations
Operating profit	£ 1,985	£ 2,239	[1]
Included within net finance costs
Net gains on derivative financial instruments	34	140
Net losses on financial assets at fair value through profit and loss	(8)	(32)
Net finance costs	(685)	(624)
Included within share of post-tax results of joint ventures and associates
Share of post-tax results of joint ventures and associates	71	51	[1]
Profit before tax	1,371	1,666	[1]
Profit after tax from continuing operations	1,064	1,219	[1],[2]
Total
Included within operating profit from continuing operations
Net gain on disposal of NECO		511
Cost efficiency programme	(39)	(61)
Transaction, separation and integration costs	(11)	(65)
IFA1 fire insurance proceeds	92	33
Net gains on commodity contract derivatives	41	65
Operating profit	83	483
Included within net finance costs
Net gains on derivative financial instruments	34	140
Net losses on financial assets at fair value through profit and loss	(8)	(32)
Net finance costs	26	108
Included within share of post-tax results of joint ventures and associates
Net gains on financial instruments	12	(19)
Share of post-tax results of joint ventures and associates	12	(19)
Profit before tax	121	572
Tax on exceptional items and remeasurements	(20)	(270)
Profit after tax from continuing operations	101	302
Exceptional items
Included within operating profit from continuing operations
Net gain on disposal of NECO		511
Cost efficiency programme	(39)	(61)
Transaction, separation and integration costs	(11)	(65)
IFA1 fire insurance proceeds	92	33
Net gains on commodity contract derivatives	0	0
Operating profit	42	418
Included within net finance costs
Net gains on derivative financial instruments	0	0
Net losses on financial assets at fair value through profit and loss	0	0
Net finance costs	0	0
Included within share of post-tax results of joint ventures and associates
Net gains on financial instruments	0	0
Share of post-tax results of joint ventures and associates	0	0
Profit before tax	42	418
Tax on exceptional items and remeasurements	1	(221)
Profit after tax from continuing operations	43	197
Remeasurements
Included within operating profit from continuing operations
Net gain on disposal of NECO		0
Cost efficiency programme	0	0
Transaction, separation and integration costs	0	0
IFA1 fire insurance proceeds	0	0
Net gains on commodity contract derivatives	41	65
Operating profit	41	65
Included within net finance costs
Net gains on derivative financial instruments	34	140
Net losses on financial assets at fair value through profit and loss	(8)	(32)
Net finance costs	26	108
Included within share of post-tax results of joint ventures and associates
Net gains on financial instruments	12	(19)
Share of post-tax results of joint ventures and associates	12	(19)
Profit before tax	79	154
Tax on exceptional items and remeasurements	(21)	(49)
Profit after tax from continuing operations	£ 58	£ 105
[1]Comparative amounts have been re-presented to reflect the classification of the Further Acquisition Agreement (the FAA option) as held for sale and within discontinued operations.[2]Comparative amounts have been re-presented to reflect the classification of the FAA option within the UK Gas Transmission business disposal group.

Exceptional items and remeasu_4

Exceptional items and remeasurements - Narrative (Details) £ in Millions, $ in Billions			1 Months Ended	6 Months Ended		23 Months Ended
	May 25, 2022 GBP (£)	May 25, 2022 USD ($)	Nov. 30, 2021 GBP (£)	Sep. 30, 2023 GBP (£)	Sep. 30, 2022 GBP (£)	Sep. 30, 2023 GBP (£)
Cost efficiency programme
Disclosure Of Exceptional Items [Line Items]
Cost efficiency programme, annual savings target			£ 400
Cost efficiency programme, period			3 years
Exceptional items
Disclosure Of Exceptional Items [Line Items]
Expense of restructuring activities				£ 39	£ 61
Transaction, separation and integration costs				11	65
Cash outflows relating to transaction, separation and integration costs				9	59
Income from insurance recovery				92	33
Cash inflows relating to insurance recovery				0	33
Gains on disposals of investments					511
Exceptional items | Cost efficiency programme
Disclosure Of Exceptional Items [Line Items]
Expense of restructuring activities				39	61	£ 142
Cash outflows relating to restructuring activities				£ 28	£ 38
Exceptional items | The Narragansett Electric Company
Disclosure Of Exceptional Items [Line Items]
Proportion of ownership interest disposed	100%	100%
Consideration received	£ 3,100	$ 3.9

Finance income and costs (Detai

Finance income and costs (Details) - GBP (£) £ in Millions	6 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Finance income
Interest income from financing activities	£ 52	£ 14
Net interest on pensions and other post-retirement benefit obligations	51	41
Net losses on financial assets at fair value through profit and loss	(8)	(32)
Other interest income	20	14
Finance income	115	37	[1]
Finance costs
Interest expense on financial instruments	(903)	(878)
Unwinding of discount on provisions	(50)	(42)
Other interest	(8)	8
Net gains on derivative financial instruments	34	140
Less: interest capitalised	127	111
Finance costs	(800)	(661)	[1]
Net finance costs	(685)	(624)
Principal accretion on inflation-linked debt	149	240
Principal accretion on inflation-linked swaps	£ 18	£ (5)
Capitalisation rate of borrowing costs eligible for capitalisation	4.70%	4.30%
Tax relief on capitalised interest	£ 21	£ 13
[1]Comparative amounts have been re-presented to reflect the classification of the Further Acquisition Agreement (the FAA option) as held for sale and within discontinued operations.

Assets held for sale and disc_3

Assets held for sale and discontinued operations - Schedule of assets and liabilities classified as held for sale (Details) - GBP (£) £ in Millions	Sep. 30, 2023	Mar. 31, 2023
Disclosure Of Detailed Information About Assets Held For Sale [Line Items]
Assets held for sale	£ 1,441	£ 1,443
Liabilities held for sale	(51)	(109)
Assets and liabilities classified as held for sale
Disclosure Of Detailed Information About Assets Held For Sale [Line Items]
Assets held for sale	1,441	1,443
Liabilities held for sale	(51)	(109)
Net assets held for sale	1,390	1,334
Assets and liabilities classified as held for sale | FAA option
Disclosure Of Detailed Information About Assets Held For Sale [Line Items]
Assets held for sale	0	0
Liabilities held for sale	0	(109)
Net assets held for sale	0	(109)
Assets and liabilities classified as held for sale | FAA forward
Disclosure Of Detailed Information About Assets Held For Sale [Line Items]
Assets held for sale	0	0
Liabilities held for sale	(7)	0
Net assets held for sale	(7)	0
Assets and liabilities classified as held for sale | RAA option
Disclosure Of Detailed Information About Assets Held For Sale [Line Items]
Assets held for sale	0	0
Liabilities held for sale	(44)	0
Net assets held for sale	(44)	0
Assets and liabilities classified as held for sale | GasT TopCo Limited
Disclosure Of Detailed Information About Assets Held For Sale [Line Items]
Assets held for sale	1,441	1,443
Liabilities held for sale	0	0
Net assets held for sale	£ 1,441	£ 1,443

Assets held for sale and disc_4

Assets held for sale and discontinued operations - Narrative (Details) - GBP (£) £ in Billions	Jul. 19, 2023	Mar. 31, 2023	Jan. 31, 2023
GasT TopCo Limited
Disclosure Of Detailed Information About Assets Held For Sale [Line Items]
Proportion of ownership interest disposed	20%
Proportion of ownership interest in associate	20%	40%	40%
GasT TopCo Limited | Consortium
Disclosure Of Detailed Information About Assets Held For Sale [Line Items]
Proportion of ownership interest in associate			60%
UK Gas Transmission
Disclosure Of Detailed Information About Assets Held For Sale [Line Items]
Proportion of ownership interest disposed			100%
Portion of consideration received			£ 4
Portion of consideration received consisting of shareholding in acquirer			40%

Assets held for sale and disc_5

Assets held for sale and discontinued operations - Summary of discontinued operations in the Income Statement (Details) - GBP (£) £ in Millions	6 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Disclosure of analysis of single amount of discontinued operations [line items]
Revenue	£ 8,489	£ 9,444	[1]
Operating profit	1,985	2,239	[1]
Finance income	115	37	[1]
Finance costs	(800)	(661)	[1]
Profit before tax	1,371	1,666	[1]
Profit/(loss) after tax from discontinued operations	65	37	[1],[2]
Discontinued operations
Disclosure of analysis of single amount of discontinued operations [line items]
Revenue	0	805
Other operating costs	0	(459)
Operating profit	0	346
Finance income	9	9
Profit before tax	70	94
Tax	5	57
Profit/(loss) after tax from discontinued operations	65	37
Discontinued operations | After exceptional items and remeasurements
Disclosure of analysis of single amount of discontinued operations [line items]
Finance costs	£ 61	£ (261)
[1]Comparative amounts have been re-presented to reflect the classification of the Further Acquisition Agreement (the FAA option) as held for sale and within discontinued operations.[2]Comparative amounts have been re-presented to reflect the classification of the FAA option within the UK Gas Transmission business disposal group.

Assets held for sale and disc_6

Assets held for sale and discontinued operations - Summary of discontinued operations in the Statement of Comprehensive Income (Details) - GBP (£) £ in Millions	6 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Disclosure of analysis of single amount of discontinued operations [line items]
Profit after tax from discontinued operations	£ 65	£ 37	[1],[2]
Items from discontinued operations that will never be reclassified to profit or loss:
Remeasurement losses on pension assets and post-retirement benefit obligations	(263)	(631)	[1]
Tax on items that will never be reclassified to profit or loss	64	159	[1]
Total items from continuing operations that will never be reclassified to profit or loss	(201)	(458)	[1]
Items from discontinued operations that may be reclassified subsequently to profit or loss:
Net gains in respect of cash flow hedges	201	450	[1]
Net gains in respect of cost of hedging	40	(64)	[1]
Net losses on investments in debt instruments measured at fair value through other comprehensive income	(16)	(47)	[1]
Tax on items that may be reclassified subsequently to profit or loss	(59)	(86)	[1]
Total items from continuing operations that may be reclassified subsequently to profit or loss	284	2,469	[1]
Other comprehensive income for the period, net of tax	74	1,925	[1]
Total comprehensive income for the period	1,203	3,181	[1]
Discontinued operations
Disclosure of analysis of single amount of discontinued operations [line items]
Profit after tax from discontinued operations	65	37
Items from discontinued operations that will never be reclassified to profit or loss:
Remeasurement losses on pension assets and post-retirement benefit obligations	0	(126)
Tax on items that will never be reclassified to profit or loss	0	31
Total items from continuing operations that will never be reclassified to profit or loss	0	(95)
Items from discontinued operations that may be reclassified subsequently to profit or loss:
Net gains in respect of cash flow hedges	0	8
Net gains in respect of cost of hedging	0	4
Net losses on investments in debt instruments measured at fair value through other comprehensive income	(12)	0
Tax on items that may be reclassified subsequently to profit or loss	3	(3)
Total items from continuing operations that may be reclassified subsequently to profit or loss	(9)	9
Other comprehensive income for the period, net of tax	(9)	(86)
Total comprehensive income for the period	£ 56	£ (49)
[1]Comparative amounts have been re-presented to reflect the classification of the FAA option within the UK Gas Transmission business disposal group.[2]Comparative amounts have been re-presented to reflect the classification of the Further Acquisition Agreement (the FAA option) as held for sale and within discontinued operations.

Tax from continuing operations

Tax from continuing operations (Details) - GBP (£) £ in Millions	6 Months Ended			12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022		Mar. 31, 2023
Income taxes paid (refund) [abstract]
Tax charge from continuing operations	£ (307)	£ (447)	[1]
Average effective tax rate	22.40%	26.80%		24.40%
[1]Comparative amounts have been re-presented to reflect the classification of the Further Acquisition Agreement (the FAA option) as held for sale and within discontinued operations.

Earnings per share (Details)

Earnings per share (Details) - GBP (£) £ / shares in Units, £ in Millions, shares in Millions	6 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Basic earnings per share [abstract]
Profit after tax from continuing operations attributable to the parent	£ 1,063	£ 1,219
Profit after tax from discontinued operations attributable to the parent	65	37
Total profit after tax attributable to the parent	£ 1,128	£ 1,256
Basic earnings per share (continuing) (in GBP per share)	£ 0.288	£ 0.334	[1]
Basic earnings per share (discontinued) (in GBP per share)	0.018	0.01
Basic earnings per share (continuing and discontinued) (in GBP per share)	£ 0.306	£ 0.344	[1]
Weighted average number of shares - basic (in shares)	3,682	3,651
Diluted earnings per share [abstract]
Profit after tax from continuing operations attributable to the parent	£ 1,063	£ 1,219
Profit after tax from discontinued operations attributable to the parent	65	37
Total profit after tax attributable to the parent	£ 1,128	£ 1,256
Diluted earnings per share (continuing) (in GBP per share)	£ 0.287	£ 0.332	[1]
Diluted earnings per share (discontinued) (in GBP per share)	0.018	0.01
Diluted earnings per share (continuing and discontinued) (in GBP per share)	£ 0.305	£ 0.342	[1]
Weighted average number of shares - diluted (in shares)	3,700	3,668
[1]Comparative amounts have been re-presented to reflect the classification of the Further Acquisition Agreement (the FAA option) as held for sale and within discontinued operations.

Dividends - Schedule of dividen

Dividends - Schedule of dividends (Details) - GBP (£) £ / shares in Units, £ in Millions	12 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Final dividend
Summary Of Dividends [Line Items]
Cash dividend paid (in GBP per share)	£ 0.3760	£ 0.3376
Cash dividend paid	£ 1,325	£ 1,119
Scrip dividend	£ 56	£ 114
Interim dividend
Summary Of Dividends [Line Items]
Cash dividend paid (in GBP per share)	£ 0.1784
Cash dividend paid	£ 488
Scrip dividend	£ 163

Dividends - Narrative (Details)

Dividends - Narrative (Details) - GBP (£) £ / shares in Units, £ in Millions	6 Months Ended	12 Months Ended
	Sep. 30, 2023	Mar. 31, 2023	Mar. 31, 2022
Summary Of Dividends [Line Items]
Dividends declared before financial statements authorised for issue (GBP per share)	£ 0.1940
Dividends declared before financial statements authorised for issue	£ 716
Final dividend
Summary Of Dividends [Line Items]
Cash dividend paid (in GBP per share)		£ 0.3760	£ 0.3376
Cash dividend paid		£ 1,325	£ 1,119
Scrip dividend		£ 56	£ 114

Fair value measurement - Schedu

Fair value measurement - Schedule of assets and liabilities measured at fair value (Details) - GBP (£) £ in Millions	Sep. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Mar. 31, 2022
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial assets	£ 2,263	£ 3,052
Financial liabilities	(1,447)	(1,312)
Total	816	1,740
Level 1
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial assets	1,007	1,764
Financial liabilities	0	0
Total	1,007	1,764
Level 2
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial assets	751	810
Financial liabilities	(1,297)	(1,131)
Total	(546)	(321)
Level 3
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial assets	505	478
Financial liabilities	(150)	(181)
Total	355	297	£ 223	£ 233
Financing derivatives
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial liabilities	(1,314)	(1,119)
Financing derivatives | Level 1
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial liabilities	0	0
Financing derivatives | Level 2
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial liabilities	(1,219)	(997)
Financing derivatives | Level 3
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial liabilities	(95)	(122)
Commodity contract derivatives
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial liabilities	(123)	(174)
Commodity contract derivatives | Level 1
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial liabilities	0	0
Commodity contract derivatives | Level 2
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial liabilities	(78)	(134)
Commodity contract derivatives | Level 3
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial liabilities	(45)	(40)
Contingent consideration
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial liabilities	(10)	(19)
Contingent consideration | Level 1
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial liabilities	0	0
Contingent consideration | Level 2
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial liabilities	0	0
Contingent consideration | Level 3
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial liabilities	(10)	(19)
Investments held at fair value through profit and loss
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial assets	1,490	2,216
Investments held at fair value through profit and loss | Level 1
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial assets	1,007	1,764
Investments held at fair value through profit and loss | Level 2
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial assets	0	0
Investments held at fair value through profit and loss | Level 3
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial assets	483	452
Investments held at fair value through other comprehensive income
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial assets	388	407
Investments held at fair value through other comprehensive income | Level 1
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial assets	0	0
Investments held at fair value through other comprehensive income | Level 2
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial assets	388	407
Investments held at fair value through other comprehensive income | Level 3
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial assets	0	0
Financing derivatives
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial assets	329	363
Financing derivatives | Level 1
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial assets	0	0
Financing derivatives | Level 2
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial assets	309	341
Financing derivatives | Level 3
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial assets	20	22
Commodity contract derivatives
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial assets	56	66
Commodity contract derivatives | Level 1
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial assets	0	0
Commodity contract derivatives | Level 2
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial assets	54	62
Commodity contract derivatives | Level 3
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial assets	£ 2	£ 4

Fair value measurement - Narrat

Fair value measurement - Narrative (Details) £ in Millions	Sep. 30, 2023 GBP (£) investment	Mar. 31, 2023 GBP (£)
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Borrowings | £	£ 44,797	£ 42,985
Number of equity investments valued based on latest transaction price	15
Number of equity investments	33
Number of equity investments valued based on internal valuation process	18
At fair value
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Borrowings | £	£ 38,354	£ 38,219

Fair value measurement - Sche_2

Fair value measurement - Schedule of impacts of reasonably possible changes in significant Level 3 assumptions (Details) - GBP (£) £ in Millions	Sep. 30, 2023	Sep. 30, 2022
Financing derivatives | +20 basis point increase in Limited Price Index (LPI) market curve
Disclosure of sensitivity analysis for actuarial assumptions [line items]
+20 basis point increase in Limited Price Index (LPI) market curve	£ (38)	£ (51)
Financing derivatives | -20 basis point decrease in LPI market curve
Disclosure of sensitivity analysis for actuarial assumptions [line items]
-20 basis point decrease in LPI market curve	38	51
Financing derivatives | +20 basis point increase between Retail Price Index (RPI) and Consumer Price Index (CPI)
Disclosure of sensitivity analysis for actuarial assumptions [line items]
+20 basis point increase between Retail Price Index (RPI) and Consumer Price Index (CPI)	36	17
Financing derivatives | -20 basis point decrease between RPI and CPI market curves
Disclosure of sensitivity analysis for actuarial assumptions [line items]
-20 basis point decrease between RPI and CPI market curves	(33)	(16)
Commodity contract derivatives | 10% increase in commodity prices
Disclosure of sensitivity analysis for actuarial assumptions [line items]
10% increase in commodity prices	15	35
Commodity contract derivatives | 10% decrease in commodity prices
Disclosure of sensitivity analysis for actuarial assumptions [line items]
10% decrease in commodity prices	(15)	(36)
Commodity contract derivatives | +10% market area price change
Disclosure of sensitivity analysis for actuarial assumptions [line items]
+10% market area price change	12	7
Commodity contract derivatives | -10% market area price change
Disclosure of sensitivity analysis for actuarial assumptions [line items]
-10% market area price change	(11)	(7)
Other | +50 basis points change in discount rate
Disclosure of sensitivity analysis for actuarial assumptions [line items]
+50 basis points change in discount rate	(8)	(9)
Other | -50 basis points change in discount rate
Disclosure of sensitivity analysis for actuarial assumptions [line items]
-50 basis points change in discount rate	9	£ 10
Other | +10% change in venture capital price
Disclosure of sensitivity analysis for actuarial assumptions [line items]
+10% change in venture capital price	30
Other | -10% change in venture capital price
Disclosure of sensitivity analysis for actuarial assumptions [line items]
-10% change in venture capital price	£ (30)

Fair value measurement - Sche_3

Fair value measurement - Schedule of reconciliation of changes in Level 3 (Details) - GBP (£) £ in Millions	6 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Changes In Fair Value Measurement, Assets (Liabilities) [Roll Forward]
Financial assets (liabilities), beginning balance	£ 1,740
Financial assets (liabilities), ending balance	816
Level 3
Changes In Fair Value Measurement, Assets (Liabilities) [Roll Forward]
Financial assets (liabilities), beginning balance	297	£ 233
Net gains/(losses) through the consolidated income statement for the period	47	150
Purchases	1	(152)
Settlements	10	(8)
Financial assets (liabilities), ending balance	355	223
Financing derivatives | Level 3
Changes In Fair Value Measurement, Assets (Liabilities) [Roll Forward]
Financial assets (liabilities), beginning balance	(100)	(187)
Net gains/(losses) through the consolidated income statement for the period	25	76
Purchases	0	(133)
Settlements	0	0
Financial assets (liabilities), ending balance	(75)	(244)
Gains (losses) recognized in P&L	25	93
Commodity contract derivatives | Level 3
Changes In Fair Value Measurement, Assets (Liabilities) [Roll Forward]
Financial assets (liabilities), beginning balance	(36)	44
Net gains/(losses) through the consolidated income statement for the period	(4)	44
Purchases	(10)	(56)
Settlements	7	(4)
Financial assets (liabilities), ending balance	(43)	28
Gains (losses) recognized in P&L	(15)	(23)
Other | Level 3
Changes In Fair Value Measurement, Assets (Liabilities) [Roll Forward]
Financial assets (liabilities), beginning balance	433	376
Net gains/(losses) through the consolidated income statement for the period	26	30
Purchases	11	37
Settlements	3	(4)
Financial assets (liabilities), ending balance	£ 473	£ 439

Net debt - Schedule of componen

Net debt - Schedule of components of net debt (Details) - GBP (£) £ in Millions	Sep. 30, 2023	Mar. 31, 2023
Disclosure of detailed information about financial instruments [line items]
Cash and cash equivalents	£ 227	£ 163
Current financial investments	1,680	2,605
Borrowings and bank overdrafts	(44,797)	(42,985)
Financing derivatives	(985)	(756)
Net debt (net of related derivative financial instruments)	(43,875)	(40,973)
Derivative liabilities	1,052	864
Derivatives | Capital expenditure
Disclosure of detailed information about financial instruments [line items]
Derivative liabilities	£ 4	£ 4

Net debt - Schedule of balance

Net debt - Schedule of balance sheet allocation of derivative balances (Details) - GBP (£) £ in Millions	Sep. 30, 2023	Mar. 31, 2023
Disclosure of detailed information about financial instruments [line items]
Derivative financial assets	£ 385	£ 429
Derivative financial liabilities	(1,437)	(1,293)
Financing derivatives	(1,052)	(864)
Financing derivatives
Disclosure of detailed information about financial instruments [line items]
Derivative financial assets	329	363
Derivative financial liabilities	(1,314)	(1,119)
Financing derivatives	(985)	(756)
Commodity contract derivatives
Disclosure of detailed information about financial instruments [line items]
Derivative financial assets	56	66
Derivative financial liabilities	(123)	(174)
Financing derivatives	£ (67)	£ (108)

Pensions and other post-retir_3

Pensions and other post-retirement benefit obligations - Schedule of defined benefit plan recognised in balance sheet (Details) - GBP (£) £ in Millions	Sep. 30, 2023	Mar. 31, 2023
Disclosure of defined benefit plans [line items]
Other post-employment liabilities	£ (67)	£ (69)
Net defined benefit asset	1,737	1,951
Assets	2,352	2,645
Liabilities	(615)	(694)
Funded obligations
Disclosure of defined benefit plans [line items]
Present value of obligations	(17,502)	(18,934)
Fair value of plan assets	19,570	21,246
Funding surplus/(deficit)	2,068	2,312
Unfunded obligations
Disclosure of defined benefit plans [line items]
Present value of obligations	£ (264)	£ (292)

Pensions and other post-retir_4

Pensions and other post-retirement benefit obligations - Schedule of key actuarial assumptions (Details)	Sep. 30, 2023	Mar. 31, 2023
UK
Disclosure of defined benefit plans [line items]
Discount rate – UK past service	5.55%	4.80%
Rate of increase in RPI – UK past service	3.19%	3.17%
US
Disclosure of defined benefit plans [line items]
Discount rate – US	5.70%	4.85%

Pensions and other post-retir_5

Pensions and other post-retirement benefit obligations - Narrative (Details) - GBP (£) £ in Millions	6 Months Ended
	Sep. 30, 2023	Mar. 31, 2023
Disclosure of defined benefit plans [line items]
Net defined benefit asset	£ 1,737	£ 1,951
Increase in net defined benefit asset	(214)
Net actuarial losses	263
Actuarial losses related to asset performance	(1,754)
Actuarial gain related to changes in actuarial assumptions	1,491
UK
Disclosure of defined benefit plans [line items]
Actuarial losses related to asset performance	(1,155)
Actuarial gain related to changes in actuarial assumptions	793
Funding surplus/(deficit)	1,377	1,672
US
Disclosure of defined benefit plans [line items]
Actuarial losses related to asset performance	(599)
Actuarial gain related to changes in actuarial assumptions	698
Funding surplus/(deficit)	£ 975	£ 973

Commitments and contingencies (

Commitments and contingencies (Details) - GBP (£) £ in Millions	Sep. 30, 2023	Mar. 31, 2023
Subclassifications of assets, liabilities and equities [abstract]
Energy purchase commitments	£ 13,824	£ 19,194
Contractual capital commitments	£ 3,218	£ 2,936

Exchange rates (Details)

Exchange rates (Details)	6 Months Ended		12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Mar. 31, 2023
Foreign exchange rates [abstract]
Closing rate applied at period end	1.22	1.12	1.23
Average rate applied for the period	1.25	1.21	1.22

Additional disclosures in res_3

Additional disclosures in respect of guaranteed securities - Narrative (Details) - GBP (£) £ in Millions		6 Months Ended
	Oct. 29, 2007	Sep. 30, 2023
National Grid plc and Niagara Mohawk Power Corporation combined
Disclosure of information about consolidated structured entities [line items]
Proceeds from issuing shares		£ 23
National Grid Gas Plc
Disclosure of information about consolidated structured entities [line items]
Preferred shares issuance rate	3.60%
British Transco Finance Inc.
Disclosure of information about consolidated structured entities [line items]
Preferred shares issuance rate	3.90%

Additional disclosures in res_4

Additional disclosures in respect of guaranteed securities - Disclosure of Combined Statement of Financial Position (Details) - GBP (£) £ in Millions	Sep. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Mar. 31, 2022
Disclosure of information about consolidated structured entities [line items]
Non-current assets	£ 86,550	£ 83,531
Current assets	7,697	9,166
Current liabilities	(8,279)	(9,130)
Non-current liabilities	(56,488)	(54,005)
Net assets	29,480	29,562
Equity	29,480	£ 29,562	£ 25,957	£ 23,856
Other subsidiaries
Disclosure of information about consolidated structured entities [line items]
Non-current assets	126
Current assets	15,557
Current liabilities	(6,893)
Non-current liabilities	(2,080)
Investments in subsidiaries reported in separate financial statements	14,480
National Grid plc and Niagara Mohawk Power Corporation combined
Disclosure of information about consolidated structured entities [line items]
Non-current assets	12,033
Current assets	1,526
Current liabilities	(1,263)
Non-current liabilities	(13,703)
Net assets	5,303
Equity	£ 5,303

Additional disclosures in res_5

Additional disclosures in respect of guaranteed securities - Disclosure of Combined Income Statement (Details) - GBP (£) £ in Millions	6 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	[1]
Disclosure of information about consolidated structured entities [line items]
Revenue	£ 8,489	£ 9,444
Operating profit	1,985	2,239
Profit after tax from continuing operations	1,064	£ 1,219	[2]
National Grid plc and Niagara Mohawk Power Corporation combined
Disclosure of information about consolidated structured entities [line items]
Revenue	1,594
Operating costs	(1,330)
Operating profit	264
Other income and costs, including taxation	(51)
Profit after tax from continuing operations	213
Other subsidiaries
Disclosure of information about consolidated structured entities [line items]
Other income from other subsidiaries	£ 0
[1]Comparative amounts have been re-presented to reflect the classification of the Further Acquisition Agreement (the FAA option) as held for sale and within discontinued operations.[2]Comparative amounts have been re-presented to reflect the classification of the FAA option within the UK Gas Transmission business disposal group.