Blackrock Financial Institutions Series Trust N-CSRS Certified semi-annual shareholder report (management investment company)

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM N-CSR

CERTIFIED SHAREHOLDER REPORT OF REGISTERED MANAGEMENT

INVESTMENT COMPANIES

Investment Company Act file number: 811-03189

Name of Fund: BlackRock Summit Cash Reserves Fund of BlackRock Financial Institutions Series Trust

Fund Address: 100 Bellevue Parkway, Wilmington, DE 19809

Name and address of agent for service: John M. Perlowski, Chief Executive Officer, BlackRock Summit Cash Reserves Fund of BlackRock Financial Institutions Series Trust, 55 East 52^nd Street, New York, NY 10055

Registrant’s telephone number, including area code: (800) 441-7762

Date of fiscal year end: 04/30/2022

Date of reporting period: 10/31/2021

Item 1 – Report to Stockholders

(a) The Report to Shareholders is attached herewith.

OCTOBER 31, 2021

2021 Semi-Annual Report

(Unaudited)

BlackRock Financial Institutions Series Trust

· BlackRock Summit Cash Reserves Fund

Not FDIC Insured • May Lose Value • No Bank Guarantee  

The Markets in Review

Dear Shareholder,

The 12-month reporting period as of October 31, 2021 was a remarkable period of adaptation and recovery, as the global economy dealt with the implications of the coronavirus (or “COVID-19”) pandemic. The United States began the reporting period as the initial reopening-led economic rebound was beginning to slow. Nonetheless, the economy continued to grow at a solid pace for the reporting period, eventually regaining the output lost from the pandemic. However, a rapid rebound in consumer spending pushed up against supply constraints and led to elevated inflation.

Equity prices rose with the broader economy, as the implementation of mass vaccination campaigns and passage of two additional fiscal stimulus packages further boosted stocks, and many equity indices neared or surpassed all-time highs late in the reporting period. In the United States, returns of small-capitalization stocks, which benefited the most from the resumption of in-person activities, outpaced large-capitalization stocks. International equities also gained, as both developed and emerging markets continued to recover from the effects of the pandemic.

The 10-year U.S. Treasury yield (which is inversely related to bond prices) had fallen sharply prior to the beginning of the reporting period, which meant bonds were priced for extreme risk avoidance and economic disruption. Despite expectations of doom and gloom, the economy expanded rapidly, stoking inflation concerns in early 2021, which led to higher yields and a negative overall return for most U.S. Treasuries. In the corporate bond market, support from the U.S. Federal Reserve (the “Fed”) assuaged credit concerns and led to solid returns for high-yield corporate bonds, outpacing investment-grade corporate bonds.

The Fed remained committed to accommodative monetary policy by maintaining near-zero interest rates and by reiterating that inflation could exceed its 2% target for a sustained period without triggering a rate increase. In response to rising inflation late in the period, the Fed changed its market guidance, raising the possibility of higher rates in 2022 and reducing bond purchasing beginning in late 2021.

Looking ahead, we believe that the global expansion will continue to broaden as Europe and other developed market economies gain momentum, although the Delta variant of the coronavirus remains a threat, particularly in emerging markets. While we expect inflation to remain elevated in the medium-term as the expansion continues, we believe the recent uptick owes more to temporary supply disruptions than a lasting change in fundamentals. The change in Fed policy also means that moderate inflation is less likely to be followed by interest rate hikes that could threaten the economic expansion.

Overall, we favor a moderately positive stance toward risk, with an overweight in equities. Sectors that are better poised to manage the transition to a lower-carbon world, such as technology and health care, are particularly attractive in the long-term. U.S. small-capitalization stocks and European equities are likely to benefit from the continuing vaccine-led restart, while Chinese equities stand to gain from a more accommodative monetary and fiscal environment as the Chinese economy slows. We are underweight long-term credit, but inflation-protected U.S. Treasuries, Asian fixed income, and emerging market local-currency bonds offer potential opportunities. We believe that international diversification and a focus on sustainability can help provide portfolio resilience, and the disruption created by the coronavirus appears to be accelerating the shift toward sustainable investments.

In this environment, our view is that investors need to think globally, extend their scope across a broad array of asset classes, and be nimble as market conditions change. We encourage you to talk with your financial advisor and visit blackrock.com for further insight about investing in today’s markets.

Sincerely,

Rob Kapito

President, BlackRock Advisors, LLC

Rob Kapito

President, BlackRock Advisors, LLC

Total Returns as of October 31, 2021
	6-Month	12-Month
U.S. large cap equities (S&P 500® Index)	10.91%	42.91%
U.S. small cap equities (Russell 2000® Index)	1.85	50.80
International equities (MSCI Europe, Australasia, Far East Index)	4.14	34.18
Emerging market equities (MSCI Emerging Markets Index)	(4.87)	16.96
3-month Treasury bills (ICE BofA 3-Month U.S. Treasury Bill Index)	0.01	0.06
U.S. Treasury securities (ICE BofA 10-Year U.S. Treasury Index)	1.59	(4.77)
U.S. investment grade bonds (Bloomberg U.S. Aggregate Bond Index)	1.06	(0.48)
Tax-exempt municipal bonds (S&P Municipal Bond Index)	0.33	2.76
U.S. high yield bonds (Bloomberg U.S. Corporate High Yield 2% Issuer Capped Index)	2.36	10.53
Past performance is not an indication of future results. Index performance is shown for illustrative purposes only. You cannot invest directly in an index.

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Table of Contents

	Page
The Markets in Review		2
Semi-Annual Report:
Money Market Overview		4
Fund Summary		5
Disclosure of Expenses		5
Financial Statements:
Schedule of Investments		6
Statement of Assets and Liabilities		8
Statement of Operations		10
Statements of Changes in Net Assets		11
Financial Highlights		12
Notes to Financial Statements		15
Disclosure of Investment Advisory Agreement		19
Additional Information		22
Glossary of Terms Used in this Report		24

3

Money Market Overview For the 6-Month Period Ended October 31, 2021

During the six-month period ended October 31, 2021, the Federal Open Market Committee (the “FOMC”) left the range for the Federal Funds target rate unchanged at 0.00% – 0.25%, which has been the range since the emergency cuts at the start of the coronavirus pandemic. Fed Chair Jerome Powell maintained the position that the recovery of the economy will depend on the course of the virus and the progress of the vaccination dissemination. In June 2021, the Fed made “technical” upward adjustments of 0.05% to the interest rate paid on excess reserves and the offering rate on overnight reverse repurchase agreement operations, bringing these “administered rates” to 0.15% and 0.05%, respectively. Fed Chair Jerome Powell noted in the press conference following the meeting that these adjustments were made “in order to keep the Federal Funds rate well within the target range and to support smooth functioning in money markets.”

By its September 2021 meeting, the FOMC noted that “if progress (toward its maximum employment and price stability goals) continues broadly as expected, the Committee judges that a moderation in the pace of asset purchases may soon be warranted.” Fed Chair Jerome Powell also acknowledged that “the timing and pace of the coming reduction in asset purchases will not be intended to carry a direct signal regarding the timing of interest-rate liftoff, for which (the Fed has) articulated a different and substantially more stringent test.” The minutes from the September 21, 2021 FOMC meeting released on October 18, 2021 mentioned that if a decision to begin tapering assets purchases was made at the November 2021 meeting, “tapering could commence” as soon as mid-November. Participants also “reaffirmed” that “a policy shift toward a moderation of asset purchases provided no direct signal about its interest rate policy.” That said, as of late October 2021, futures contracts for Federal Funds were priced for approximately two 0.25% rate hikes during 2022, with a high probability of “liftoff” occurring as soon as September 2022.

In addition, the federal debt ceiling situation remained front and center during the period. The U.S. Treasury continues to employ accounting “maneuvers” known as “extraordinary measures” to fund the U.S. government following the expiration of the suspension of the debt ceiling at the end of July 2021. U.S. Treasury Secretary Janet Yellen estimated that the “Treasury is likely to exhaust its extraordinary measures if Congress has not acted to raise or suspend the debt limit by October 18.” Yields on U.S. Treasury bills (“T-bills”) maturing around this so-called “X-date” were moderately elevated relative to nearby issues in late September 2021. However, Congress passed a continuing resolution to fund the U.S. government until December 3, 2021; however, this “stop-gap” spending bill did not address the debt ceiling, which will need to be either re-suspended or raised in the next few weeks.

With the debt ceiling yet to be resolved, net T-bill issuance fell $673 billion over the last six-month period ended October 31, 2021. This reduction exacerbated the painful supply-demand imbalance in the front-end of the market. Further, liquidity in the banking system remained ample given ongoing asset purchases by the Fed and a sizable contraction in the Treasury General Account (“TGA”) of more than $1 trillion since the end of 2020.

As of October 31, 2021, the Secured Overnight Financing Rate (“SOFR”) – a broad measure of the cost of borrowing cash overnight collateralized by U.S. Treasuries – held steady at 0.05%. SOFR has been unchanged at 0.05% since the Fed’s technical adjustments in June 2021. Before that, SOFR had been pegged at 0.01% since March 2021.

The near-term outlook for U.S. money market funds remains challenged by the debt ceiling, continued accommodative monetary policy and the overall paying down of U.S. Treasury bills. Once the debt ceiling impasse has been resolved, we do expect the supply of U.S. Treasury bills to increase as the U.S. Treasury will look to build back cash in their TGA. Yield moves further out the curve will be dependent on the FOMC’s position regarding inflation and the potential for interest rate hikes in 2022.

Past performance is not an indication of future results. Index performance is shown for illustrative purposes only. You cannot invest directly in an index.

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Fund Summary  as of October 31, 2021 BlackRock Summit Cash Reserves Fund

Investment Objective

BlackRock Summit Cash Reserves Fund’s (the “Fund”) investment objective is to seek current income, preservation of capital and liquidity available from investing in a diversified portfolio of short-term money market securities.

CURRENT SEVEN-DAY YIELDS

	7-Day SEC Yield			7-Day Yield
Institutional		0.00	%		0.00	%
Investor A		0.01			0.01
Investor C		0.02			0.02

The 7-Day SEC Yield may differ from the 7-Day Yield shown above due to the fact that the 7-Day SEC Yield excludes distributed capital gains.

Past performance is not indicative of future results.

PORTFOLIO ALLOCATION

Asset Type	Percent of Net Assets
U.S. Treasury Obligations		36	%
Repurchase Agreements		35
U.S. Government Sponsored Agency Obligations		31
Liabilities in Excess of Other Assets		(2	)

Disclosure of Expenses

Shareholders of the Fund may incur the following charges: (a) transactional expenses, such as sales charges; and (b) operating expenses, including investment advisory fees, service and distribution fees, and other fund expenses. The expense example shown (which is based on a hypothetical investment of $1,000 invested on May 1, 2021 and held through October 31, 2021) is intended to assist shareholders both in calculating expenses based on an investment in the Fund and in comparing these expenses with similar costs of investing in other mutual funds.

The expense example provides information about actual account values and actual expenses. In order to estimate the expenses a shareholder paid during the period covered by this report, shareholders can divide their account value by $1,000 and then multiply the result by the number corresponding to their share class under the heading entitled “Expenses Paid During the Period.”

The expense example also provides information about hypothetical account values and hypothetical expenses based on the Fund’s actual expense ratio and an assumed rate of return of 5% per year before expenses. In order to assist shareholders in comparing the ongoing expenses of investing in the Fund and other funds, compare the 5% hypothetical example with the 5% hypothetical examples that appear in shareholder reports of other funds.

The expenses shown in the expense example are intended to highlight shareholders’ ongoing costs only and do not reflect transactional expenses, such as sales charges, if any. Therefore, the hypothetical example is useful in comparing ongoing expenses only and will not help shareholders determine the relative total expenses of owning different funds. If these transactional expenses were included, shareholder expenses would have been higher.

Expense Example

	Actual							Hypothetical(a)
		Beginning Account Value (05/01/21)		Ending Account Value (10/31/21)		Expenses Paid During the Period	(b)		Beginning Account Value (05/01/21)		Ending Account Value (10/31/21)		Expenses Paid During the Period	(b)	Annualized Expense Ratio
Institutional	$	1,000.00	$	1,000.00	$	0.35		$	1,000.00	$	1,024.85	$	0.36		0.07	%
Investor A		1,000.00		1,000.10		0.30			1,000.00		1,024.90		0.31		0.06
Investor C		1,000.00		1,000.10		0.30			1,000.00		1,024.90		0.31		0.06

^(a) Hypothetical 5% annual return before expenses is calculated by prorating the number of days in the most recent fiscal half year divided by 365.

^(b)  For each class of the Fund, expenses are equal to the annualized expense ratio for the class, multiplied by the average account value over the period, multiplied by 184/365 (to reflect the one-half year period shown).

F U N D   S U M M A R Y   /   D I S C L O S U R E  O F  E X P E N S E S 5

Schedule of Investments  (unaudited) October 31, 2021 BlackRock Summit Cash Reserves Fund (Percentages shown are based on Net Assets)

Security	Par (000)		Value
Short-Term Securities
U.S. Government Sponsored Agency Obligations — 31.3%
Fannie Mae Variable Rate Notes(a)
(SOFR + 0.35%), 0.40%, 04/07/22	$	4,120	$	4,120,000
(SOFR + 0.39%), 0.44%, 04/15/22		2,805		2,805,000
Federal Farm Credit Bank Variable Rate Notes
0.07%, 08/10/22		1,600		1,599,894
(1 mo. LIBOR US + 0.11%), 0.19%, 11/12/21(a)		390		390,000
(3 mo. Treasury money market yield + 0.15%), 0.21%, 12/13/21(a)		900		899,897
(3 mo. Treasury money market yield + 0.28%), 0.34%, 02/08/22(a)		3,000		3,000,000
(Fed Funds Rate + 0.18%), 0.26%, 07/20/22(a)		5,720		5,719,595
(SOFR + 0.03%), 0.08%, 01/12/23(a)		3,775		3,774,771
(SOFR + 0.04%), 0.09%, 07/11/22(a)		2,435		2,435,341
(SOFR + 0.05%), 0.10%, 09/08/22 - 02/17/23(a)		4,405		4,405,324
(SOFR + 0.06%), 0.11%, 10/21/22(a)		3,560		3,560,000
(SOFR + 0.08%), 0.13%, 10/14/22 - 11/03/22(a)		4,460		4,460,000
(SOFR + 0.10%), 0.15%, 09/02/22(a)		730		730,000
(SOFR + 0.18%), 0.23%, 01/14/22(a)		1,480		1,480,000
(SOFR + 0.19%), 0.24%, 11/18/21(a)		650		650,000
Federal Farm Credit Discount Notes(b)
0.09%, 11/17/21		3,545		3,544,858
0.10%, 12/02/21		1,195		1,194,897
0.08%, 12/28/21 - 01/28/22		3,150		3,149,447
0.05%, 04/19/22		2,810		2,809,340
0.06%, 06/21/22		1,780		1,779,312
Federal Home Loan Bank Discount Notes(b)
0.05%, 11/05/21 - 03/11/22		3,865		3,864,686
0.04%, 12/01/21 - 04/01/22		22,830		22,827,984
0.06%, 04/22/22		4,445		4,443,811
Federal Home Loan Bank Notes
0.05%, 11/12/21 - 02/07/22		14,190		14,189,983
0.04%, 01/12/22 - 02/01/22		7,515		7,514,814
0.06%, 05/23/22		1,820		1,819,944
(SOFR + 0.01%), 0.06%, 03/28/22 - 09/06/22(a)		3,100		3,100,000
(SOFR + 0.02%), 0.07%, 04/12/22 - 12/16/22(a)		10,005		10,005,000
(SOFR + 0.07%), 0.12%, 04/28/22(a)		780		780,000
(SOFR + 0.12%), 0.17%, 02/28/22(a)		2,100		2,100,000

Security	Par (000)		Value
U.S. Government Sponsored Agency Obligations (continued)
Federal Home Loan Mortgage Corp. 0.13%, 07/25/22	$	1,660	$	1,660,535
(SOFR + 0.07%), 0.12%, 11/10/22(a)		1,240		1,240,000
(SOFR + 0.18%), 0.23%, 12/13/21(a)		2,655		2,655,000
(SOFR + 0.20%), 0.25%, 03/11/22(a)		1,435		1,435,000
				130,144,433
U.S. Treasury Obligations — 35.9%
U.S. Treasury Bills(b)
0.05%, 11/16/21 - 02/01/22		66,524		66,519,045
0.06%, 11/26/21 - 02/03/22		38,865		38,861,981
0.04%, 12/16/21 - 12/30/21		16,737		16,735,853
0.09%, 12/16/21		10,000		9,998,875
0.11%, 12/30/21		9,300		9,298,323
0.08%, 09/08/22		1,362		1,361,118
U.S. Treasury Floating Rate Note, (3 mo. Treasury money market yield + 0.05%), 0.10%, 01/31/23(a)		5,000		5,000,000
U.S. Treasury Notes
2.50%, 02/15/22		110		110,768
1.75%, 02/28/22 - 06/15/22		210		211,634
0.38%, 03/31/22		110		110,127
2.13%, 05/15/22		750		758,229
0.13%, 06/30/22		335		335,120
				149,301,073
Total Short-Term Securities — 67.2% (Cost: $279,445,506)				279,445,506
Total Repurchase Agreements — 34.4% (Cost: $143,000,000)				143,000,000
Total Investments — 101.6% (Cost: $422,445,506(c))				422,445,506
Liabilities in Excess of Other Assets — (1.6)%				(6,820,005	)
Net Assets — 100.0%			$	415,625,501

^(a)  Variable rate security. Interest rate resets periodically. The rate shown is the effective interest rate as of period end. Security description also includes the reference rate and spread if published and available.

^(b)  Rates are discount rates or a range of discount rates as of period end.

^(c)  Cost for U.S. federal income tax purposes.

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Schedule of Investments  (unaudited) (continued) October 31, 2021 BlackRock Summit Cash Reserves Fund

Repurchase Agreements

	Repurchase Agreements												Collateral
Counterparty	Coupon Rate			Purchase Date		Maturity Date		Par (000)		At Value (000)		Proceeds Including Interest	Position	Original Par	Position Received, at Value
BNP Paribas S.A.		0.05	%		10/31/21		11/01/21	$	25	$	25,000	$25,000,035	U.S. Treasury Obligation, 0.00% to 2.63%, due 01/11/22 to 02/15/48	$24,680,727	$	25,500,000
J.P. Morgan Securities LLC		0.05			10/31/21		11/01/21		30		30,000	30,000,042	U.S. Treasury Obligation, 0.00% to 0.00%, due 11/15/21	30,602,200		30,600,119
Merrill Lynch, Pierce, Fenner & Smith, Inc.		0.05			10/31/21		11/01/21		10		10,000	10,000,014	U.S. Treasury Obligation, 0.13% to 3.00%, due 06/30/22 to 09/30/25	30,106,800		10,200,000
		0.05			10/31/21		11/01/21		20		20,000	20,000,028	U.S. Treasury Obligation, 0.13% to 3.00%, due 06/30/22 to 09/30/25	30,106,800		20,400,098
Total Merrill Lynch, Pierce, Fenner & Smith, Inc.										$	30,000				$	30,600,098
Mizuho Securities USA, Inc.		0.05			10/31/21		11/01/21		28		28,000	28,000,039	U.S. Treasury Obligation, 1.00% to 3.00%, due 11/20/50 to 09/20/51	67,483,039		29,400,000
TD Securities (USA) LLC		0.05			10/31/21		11/01/21		30		30,000	30,000,042	U.S. Treasury Obligation, 2.00% to 2.00%, due 06/30/24	29,394,100		30,600,025
										$	143,000				$	146,700,242

Fair Value Hierarchy as of Period End

Various inputs are used in determining the fair value of financial instruments. For a description of the input levels and information about the Fund’s policy regarding valuation of financial instruments, refer to the Notes to Financial Statements.

The following table summarizes the Fund’s financial instruments categorized in the fair value hierarchy. The breakdown of the Fund’s financial instruments into major categories is disclosed in the Schedule of Investments above.

	Level 1		Level 2		Level 3		Total
Assets
Investments
Short-Term Securities
Repurchase Agreements	$	—	$	143,000,000	$	—	$	143,000,000
U.S. Government Sponsored Agency Obligations		—		130,144,433		—		130,144,433
U.S. Treasury Obligations		—		149,301,073		—		149,301,073
	$	—	$	422,445,506	$	—	$	422,445,506

See notes to financial statements.

S C H E D U L E   O F   I N V E S  T M E N T S 7

Statement of Assets and Liabilities  (unaudited)

October 31, 2021

	BlackRock Summit Cash Reserves Fund
ASSETS
Investments, at value — unaffiliated(a)		$	279,445,506
Cash			154,190
Repurchase agreements, at value(b)			143,000,000
Receivables:
Capital shares sold			1,195,241
Interest — unaffiliated			24,824
Prepaid expenses			51,563
Total assets			423,871,324
LIABILITIES
Payables:
Investments purchased			7,550,482
Accounting services fees			25,968
Capital shares redeemed			545,320
Custodian fees			24,715
Income dividend distributions			379
Investment advisory fees			1,285
Trustees’ and Officer’s fees			3,480
Other accrued expenses			20,386
Other affiliate fees			2,432
Professional fees			19,923
Transfer agent fees			51,453
Total liabilities			8,245,823
NET ASSETS		$	415,625,501
NET ASSETS CONSIST OF
Paid-in capital		$	415,600,854
Accumulated earnings			24,647
NET ASSETS		$	415,625,501
(a) Investments, at cost — unaffiliated		$	279,445,506
(b) Repurchase agreements, at cost		$	143,000,000

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Statement of Assets and Liabilities  (unaudited) (continued)

October 31, 2021

	BlackRock Summit Cash Reserves Fund
NET ASSET VALUE
Institutional
Net assets		$	88,147,876
Shares outstanding			88,183,783
Net asset value		$	1.00
Shares authorized			Unlimited
Par value		$	0.10
Investor A
Net assets		$	326,765,805
Shares outstanding			326,900,201
Net asset value		$	1.00
Shares authorized			Unlimited
Par value		$	0.10
Investor C
Net assets		$	711,820
Shares outstanding			712,112
Net asset value		$	1.00
Shares authorized			Unlimited
Par value		$	0.10

See notes to financial statements.

F I N A N C I A L  S T A T E M E N T S 9

Statement of Operations  (unaudited)

Six Months Ended October 31, 2021

	BlackRock Summit Cash Reserves Fund
INVESTMENT INCOME
Interest — unaffiliated		$	157,867
Total investment income			157,867
EXPENSES
Investment advisory			1,055,229
Transfer agent — class specific			74,322
Professional			50,431
Registration			49,847
Accounting services			12,308
Custodian			10,223
Trustees and Officer			4,824
Distribution — class specific			3,524
Miscellaneous			29,057
Total expenses			1,289,765
Less:
Fees waived and/or reimbursed by the Manager			(1,088,283	)
Distribution fees waived and/or reimbursed — class specific			(3,524	)
Transfer agent fees waived and/or reimbursed — class specific			(74,322	)
Total expenses after fees waived and/or reimbursed			123,636
Net investment income			34,231
REALIZED AND UNREALIZED GAIN (LOSS)
Net realized gain from:
Investments — unaffiliated			4,446
			4,446
Net realized and unrealized gain			4,446
NET INCREASE IN NET ASSETS RESULTING FROM OPERATIONS		$	38,677

See notes to financial statements.

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Statements of Changes in Net Assets

	BlackRock Summit Cash Reserves Fund
	Six Months Ended 10/31/21 (unaudited)				Year Ended 04/30/21
INCREASE (DECREASE) IN NET ASSETS
OPERATIONS
Net investment income		$	34,231			$	17,279
Net realized gain			4,446				1,617
Net increase in net assets resulting from operations			38,677				18,896
DISTRIBUTIONS TO SHAREHOLDERS(a)
Institutional			(2,930	)			(32,481	)
Investor A			(31,025	)			(148,560	)
Investor C			(80	)			(481	)
Decrease in net assets resulting from distributions to shareholders			(34,035	)			(181,522	)
CAPITAL SHARE TRANSACTIONS
Net decrease in net assets derived from capital share transactions			(19,410,701	)			(70,239,724	)
NET ASSETS
Total decrease in net assets			(19,406,059	)			(70,402,350	)
Beginning of period			435,031,560				505,433,910
End of period		$	415,625,501			$	435,031,560

^(a) Distributions for annual periods determined in accordance with U.S. federal income tax regulations.

See notes to financial statements.

F I N A N C I A L  S T A T E M E N T S 11

Financial Highlights

(For a share outstanding throughout each period)

	BlackRock Summit Cash Reserves Fund
	Institutional
		Six Months Ended								Period from
		10/31/21 (unaudited)					Year Ended 04/30/21			07/15/19 to 04/30/20	(a)
Net asset value, beginning of period			$	1.00		$	1.00		$	1.00
Net investment income.				0.0000	(b)		0.0000	(b)		0.0098
Net realized and unrealized gain				0.0000	(b)		0.0003			0.0000	(b)
Net increase from investment operations				0.0000			0.0003			0.0098
Distributions(c)
From net investment income				(0.0000	)(d)		(0.0000	)(d)		(0.0098	)
From net realized gain				—			(0.0003	)		(0.0000	)(d)
Total distributions				(0.0000	)		(0.0003	)		(0.0098	)
Net asset value, end of period			$	1.00		$	1.00		$	1.00
Total Return(e)
Based on net asset value				0.00	%(f)		0.03	%		0.98	%(f)
Ratios to Average Net Assets
Total expenses				0.61	%(g)		0.61	%		0.64	%(g)(h)
Total expenses after fees waived and/or reimbursed				0.07	%(g)		0.17	%		0.42	%(g)(h)
Net investment income				0.01	%(g)		0.00	%(i)		1.20	%(g)
Supplemental Data
Net assets, end of period (000)			$	88,148		$	87,699		$	97,718

^(a)  Commencement of operations.

^(b)  Amount is less than $0.00005 per share.

^(c)  Distributions for annual periods determined in accordance with U.S. federal income tax regulations.

^(d)  Amount is greater than $(0.00005) per share.

^(e)  Where applicable, assumes the reinvestment of distributions.

^(f)  Aggregate total return.

^(g) Annualized.

^(h)  Includes non-recurring expenses of offering, organization and reorganization costs. Without these costs, total expenses and total expenses after fees waived and/or reimbursed would have been 0.62% and 0.39% for the period ended 04/30/2020, respectively.

⁽ⁱ⁾  Amount is less than 0.005%.

See notes to financial statements.

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Financial Highlights  (continued)

(For a share outstanding throughout each period)

	BlackRock Summit Cash Reserves Fund (continued)
	Investor A
	Six Months Ended 10/31/21				Year Ended April 30,
	(unaudited)				2021			2020			2019			2018			2017
Net asset value, beginning of period		$	1.00		$	1.00		$	1.00		$	1.00		$	1.00		$	1.00
Net investment income.			0.0001			0.0000	(a)		0.0142			0.0135			0.0025			0.0000	(a)
Net realized and unrealized gain			0.0000	(a)		0.0003			0.0000	(a)		0.0000	(a)		0.0001			0.0000	(a)
Net increase from investment operations			0.0001			0.0003			0.0142			0.0135			0.0026			0.0000
Distributions(b)
From net investment income			(0.0001	)		(0.0000	)(c)		(0.0142	)		(0.0135	)		(0.0025	)		(0.0000	)(c)
From net realized gain			—			(0.0003	)		(0.0000	)(c)		(0.0000	)(c)		(0.0001	)		(0.0000	)(c)
Total distributions			(0.0001	)		(0.0003	)		(0.0142	)		(0.0135	)		(0.0026	)		(0.0000	)
Net asset value, end of period		$	1.00		$	1.00		$	1.00		$	1.00		$	1.00		$	1.00
Total Return(d)
Based on net asset value			0.01	%(e)		0.04	%		1.43	%		1.35	%		0.26	%		0.00	%
Ratios to Average Net Assets
Total expenses			0.61	%(f)		0.60	%		0.64	%(g)		0.82	%(g)		0.93	%		0.81	%
Total expenses after fees waived and/or reimbursed			0.06	%(f)		0.17	%		0.42	%(g)		0.52	%(g)		0.93	%		0.51	%
Net investment income			0.02	%(f)		0.00	%(h)		1.36	%		1.86	%		0.25	%		0.00	%
Supplemental Data
Net assets, end of period (000)		$	326,766		$	346,281		$	405,760		$	319,960		$	45,365		$	55,609

^(a)  Amount is less than $0.00005 per share.

^(b)  Distributions for annual periods determined in accordance with U.S. federal income tax regulations.

^(c)  Amount is greater than $(0.00005) per share.

^(d)  Where applicable, assumes the reinvestment of distributions.

^(e)  Aggregate total return.

^(f)  Annualized.

^(g)  Includes non-recurring expenses of offering, organization and reorganization costs. Without these costs, total expenses and total expenses after fees waived and/or reimbursed would have been 0.61% and 0.40% for the year ended 04/30/20, respectively, and 0.72% and 0.42% for the year ended 04/30/19, respectively.

^(h)  Amount is less than 0.005%.

See notes to financial statements.

F I N A N C I A L  H I G H L I G H T S 13

Financial Highlights  (continued)

(For a share outstanding throughout each period)

	BlackRock Summit Cash Reserves Fund (continued)
	Investor C
		Six Months Ended 10/31/21				Year Ended April 30,								Period from 08/10/18	(a)
	(unaudited)						2021			2020			to 04/30/19
Net asset value, beginning of period			$	1.00			$	1.00		$	1.00		$	1.00
Net investment income				0.0001				0.0000	(b)		0.0075			0.0058
Net realized and unrealized gain				0.0000	(b)			0.0003			0.0000	(b)		0.0000	(b)
Net increase from investment operations				0.0001				0.0003			0.0075			0.0058
Distributions(c)
From net investment income				(0.0001	)			(0.0000	)(d)		(0.0075	)		(0.0058	)
From net realized gain				—				(0.0003	)		(0.0000	)(d)		(0.0000	)(d)
Total distributions				(0.0001	)			(0.0003	)		(0.0075	)		(0.0058	)
Net asset value, end of period			$	1.00			$	1.00		$	1.00		$	1.00
Total Return(e)
Based on net asset value				0.01	%(f)			0.04	%		0.75	%		0.58	%(f)
Ratios to Average Net Assets
Total expenses				1.38	%(g)			1.38	%		1.52	%(h)		1.47	%(g)(h)
Total expenses after fees waived and/or reimbursed				0.06	%(g)			0.20	%		0.90	%(h)		1.20	%(g)(h)
Net investment income				0.02	%(g)			0.00	%(i)		0.51	%		1.25	%(g)
Supplemental Data
Net assets, end of period (000)			$	712			$	1,052		$	1,956		$	651

^(a)  Commencement of operations.

^(b)  Amount is less than $0.00005 per share.

^(c)  Distributions for annual periods determined in accordance with U.S. federal income tax regulations.

^(d)  Amount is greater than $(0.00005) per share.

^(e)  Where applicable, excludes the effects of any sales charges and assumes the reinvestment of distributions.

^(f)  Aggregate total return.

^(g) Annualized.

^(h)  Includes non-recurring expenses of offering, organization and reorganization costs. Without these costs, total expenses and total expenses after fees waived and/or reimbursed would have been 1.49% and 0.87% for the year ended 04/30/20, respectively, and 1.38% and 1.11% for the period ended 04/30/19, respectively.

⁽ⁱ⁾  Amount is less than 0.005%.

See notes to financial statements.

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Notes to Financial Statements  (unaudited)

1.   ORGANIZATION

BlackRock Financial Institutions Series Trust (the “Trust”) is registered under the Investment Company Act of 1940, as amended (the “1940 Act”), as an open-end management investment company. The Trust is organized as a Massachusetts business trust. BlackRock Summit Cash Reserves Fund (the “Fund”) is a series of the Trust. The Fund is classified as diversified.

The Fund offers multiple classes of shares. All classes of shares have identical voting, dividend, liquidation and other rights and are subject to the same terms and conditions, except that certain classes bear expenses related to the shareholder servicing and distribution of such shares. Institutional Shares are sold without a sales charge and only to certain eligible investors. Investor A and Investor C Shares may be subject to a contingent deferred sales charge (“CDSC”). Investor A Shares are generally available through financial intermediaries. Investor C Shares are available only through exchanges and dividend and capital gain reinvestments by current holders. Investor C Shares automatically convert to Investor A Shares after approximately eight years. Each class has exclusive voting rights with respect to matters relating to its shareholder servicing and distribution expenditures.

The Fund operates as a “government money market fund” under Rule 2a-7 under the 1940 Act. The Fund is not subject to liquidity fees or temporary suspensions of redemptions due to declines in the Fund’s weekly liquid assets.

The Fund, together with certain other registered investment companies advised by BlackRock Advisors, LLC (the “Manager”) or its affiliates, is included in a complex of equity, multi-asset, index and money market funds referred to as the BlackRock Multi-Asset Complex.

2.   SIGNIFICANT ACCOUNTING POLICIES

The financial statements are prepared in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”), which may require management to make estimates and assumptions that affect the reported amounts of assets and liabilities in the financial statements, disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of increases and decreases in net assets from operations during the reporting period. Actual results could differ from those estimates. The Fund is considered an investment company under U.S. GAAP and follows the accounting and reporting guidance applicable to investment companies. Below is a summary of significant accounting policies:

Investment Transactions and Income Recognition: For financial reporting purposes, investment transactions are recorded on the dates the transactions are executed. Realized gains and losses on investment transactions are determined using the specific identification method. Interest income, including amortization and accretion of premiums and discounts on debt securities, is recognized daily on an accrual basis. Income, expenses and realized and unrealized gains and losses are allocated daily to each class based on its relative net assets.

Distributions: Distributions from net investment income are declared daily and paid monthly. Distributions of capital gains are distributed at least annually and are recorded on the ex-dividend dates. The character and timing of distributions are determined in accordance with U.S. federal income tax regulations, which may differ from U.S. GAAP.

Offering Costs: Offering costs are amortized over a 12-month period beginning with the commencement of operations of a class of shares.

Indemnifications: In the normal course of business, the Fund enters into contracts that contain a variety of representations that provide general indemnification. The Fund’s maximum exposure under these arrangements is unknown because it involves future potential claims against the Fund, which cannot be predicted with any certainty.

Other: Expenses directly related to the Fund or its classes are charged to the Fund or the applicable class. Expenses directly related to the Fund and other shared expenses prorated to the Fund are allocated daily to each class based on its relative net assets or other appropriate methods. Other operating expenses shared by several funds, including other funds managed by the Manager, are prorated among those funds on the basis of relative net assets or other appropriate methods.

3.   INVESTMENT VALUATION AND FAIR VALUE MEASUREMENTS

Investment Valuation Policies: U.S. GAAP defines fair value as the price the Fund would receive to sell an asset or pay to transfer a liability in an orderly transaction between market participants at the measurement date. The Fund’s investments are valued under the amortized cost method which approximates current market value in accordance with Rule 2a-7 under the 1940 Act. Under this method, investments are valued at cost when purchased and, thereafter, a constant proportionate accretion of discounts and amortization of premiums are recorded until the maturity of the security. The Fund seeks to maintain its net asset value (“NAV”) per share at $1.00, although there is no assurance that it will be able to do so on a continuing basis.

Fair Value Hierarchy: Various inputs are used in determining the fair value of financial instruments. These inputs to valuation techniques are categorized into a fair value hierarchy consisting of three broad levels for financial reporting purposes as follows:

• Level 1 – Unadjusted price quotations in active markets/exchanges for identical assets or liabilities that the Fund has the ability to access;

• Level 2 – Other observable inputs (including, but not limited to, quoted prices for similar assets or liabilities in markets that are active, quoted prices for identical or similar assets or liabilities in markets that are not active, inputs other than quoted prices that are observable for the assets or liabilities (such as interest rates, yield curves, volatilities, prepayment speeds, loss severities, credit risks and default rates) or other market–corroborated inputs); and

• Level 3 – Unobservable inputs based on the best information available in the circumstances, to the extent observable inputs are not available (including the BlackRock Global Valuation Methodologies Committee’s (the “Global Valuation Committee’s”) assumptions used in determining the fair value of financial instruments).

N O T E S  T O  F I N A N C I A L  S T A T E M E N T S 15

Notes to Financial Statements  (unaudited) (continued)

The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1 measurements) and the lowest priority to unobservable inputs (Level 3 measurements). Accordingly, the degree of judgment exercised in determining fair value is greatest for instruments categorized in Level 3. The inputs used to measure fair value may fall into different levels of the fair value hierarchy. In such cases, for disclosure purposes, the fair value hierarchy classification is determined based on the lowest level input that is significant to the fair value measurement in its entirety. The categorization of a value determined for financial instruments is based on the pricing transparency of the financial instruments and is not necessarily an indication of the risks associated with investing in those securities.

4.   SECURITIES AND OTHER INVESTMENTS

Repurchase Agreements: Repurchase agreements are commitments to purchase a security from a counterparty who agrees to repurchase the same security at a mutually agreed upon date and price. On a daily basis, the counterparty is required to maintain collateral subject to the agreement and in value no less than the agreed upon repurchase amount. Repurchase agreements may be traded bilaterally, in a tri-party arrangement or may be centrally cleared through a sponsoring agent. Subject to the custodial undertaking associated with a tri-party repurchase arrangement and for centrally cleared repurchase agreements, a third-party custodian maintains accounts to hold collateral for a fund and its counterparties. Typically, a fund and counterparty are not permitted to sell, re-pledge or use the collateral absent a default by the counterparty or the fund, respectively.

In the event the counterparty defaults and the fair value of the collateral declines, a fund could experience losses, delays and costs in liquidating the collateral.

Repurchase agreements are entered into by a fund under Master Repurchase Agreements (each, an “MRA”). The MRA permits the fund, under certain circumstances including an event of default (such as bankruptcy or insolvency), to offset payables and/or receivables with collateral held by and/or posted to the counterparty. As a result, one single net payment is created. Bankruptcy or insolvency laws of a particular jurisdiction may impose restrictions on or prohibitions against such a right of offset in the event of the MRA counterparty’s bankruptcy or insolvency. Based on the terms of the MRA, the fund receives collateral with a market value in excess of the repurchase price at maturity. Upon a bankruptcy or insolvency of the MRA counterparty, the fund would recognize a liability with respect to such excess collateral. The liability reflects the fund’s obligation under bankruptcy law to return the excess to the counterparty.

5.   INVESTMENT ADVISORY AGREEMENT AND OTHER TRANSACTIONS WITH AFFILIATES

Investment Advisory: The Trust, on behalf of the Fund, entered into an Investment Advisory Agreement with the Manager, the Fund’s investment adviser and an indirect, wholly-owned subsidiary of BlackRock, Inc. (“BlackRock”), to provide investment advisory and administrative services. The Manager is responsible for the management of the Fund’s portfolio and provides the personnel, facilities, equipment and certain other services necessary to the operations of the Fund.

For such services, the Fund pays the Manager a monthly fee at an annual rate equal to 0.50% of the average daily value of the Fund’s net assets.

For the six months ended October 31, 2021, the Fund reimbursed the Manager for certain accounting services, which is included in accounting services in the Statement of Operations. The reimbursements were $1,038.

Distribution Fees:

The Trust, on behalf of the Fund, entered into a Distribution Agreement and a Distribution Plan with BlackRock Investments, LLC (“BRIL”), an affiliate of the Manager. Pursuant to the Distribution Plan and in accordance with Rule 12b-1 under the 1940 Act, the Fund pays BRIL ongoing distribution fees. The fees are accrued daily and paid monthly at annual rates based upon the average daily net assets of the relevant share class of the Fund as follows:

Share Class	Distribution Fees
Investor C		0.75	%

BRIL and broker-dealers, pursuant to sub-agreements with BRIL, provide shareholder distribution services to the Fund. The ongoing distribution fee compensates BRIL and each broker-dealer for providing shareholder distribution related services to shareholders.

For the six months ended October 31, 2021, the following table shows the class specific distribution fees borne directly by each share class of the Fund:

	Investor C
Distribution fees — class specific	$	3,524

Transfer Agent: Pursuant to written agreements, certain financial intermediaries, some of which may be affiliates, provide the Fund with sub-accounting, recordkeeping, sub-transfer agency and other administrative services with respect to servicing of underlying investor accounts. For these services, these entities receive an asset-based fee or an annual fee per shareholder account, which will vary depending on share class and/or net assets. For the six months ended October 31, 2021, the Fund did not pay any amounts to affiliates in return for these services.

The Manager maintains a call center that is responsible for providing certain shareholder services to the Fund. Shareholder services include responding to inquiries and processing purchases and sales based upon instructions from shareholders. For the six months ended October 31, 2021, the Fund reimbursed the Manager the following amounts for costs incurred in running the call center, which are included in transfer agent — class specific in the Statement of Operations:

Fund Name	Investor A
BlackRock Summit Cash Reserves Fund	$	6,308

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Notes to Financial Statements  (unaudited) (continued)

For the six months ended October 31, 2021, the following table shows the class specific transfer agent fees borne directly by each share class of the Fund:

	Institutional		Investor A		Investor C		Total
Transfer agent fees — class specific	$	14,997	$	59,084	$	241	$	74,322

Other Fees: For the six months ended October 31, 2021, affiliates received CDSCs of $7,140 for Investor A Shares.

Expense Limitations, Waivers and Reimbursements: With respect to the Fund, the Manager contractually agreed to waive and/or reimburse fees or expenses in order to limit expenses, excluding interest expense, dividend expense, tax expense, acquired fund fees and expenses, and certain other fund expenses, which constitute extraordinary expenses not incurred in the ordinary course of the Fund’s business (“expense limitation”). The expense limitation as a percentage of average daily net assets is as follows:

Share Class	Expense Limitation
Institutional		0.42	%
Investor A		0.42
Investor C		1.17

The Manager has agreed not to reduce or discontinue the contractual expense limitations through June 30, 2023, unless approved by the Board, including a majority of the trustees who are not “interested persons” of the Trust, as defined in the 1940 Act (“Independent Trustees”), or by a vote of a majority of the outstanding voting securities of the Fund. For the six months ended October 31, 2021, the Manager waived and/or reimbursed $347,698 which is included in fees waived and/or reimbursed by the Manager in the Statement of Operations.

These amounts waived and/or reimbursed are included in Distribution fees waived and/or reimbursed — class specific and transfer agent fees waived and/or reimbursed — class specific in the Statement of Operations. For the six months ended October 31, 2021, class specific expense waivers and/or reimbursements are as follows:

	Investor C
Distribution fees waived and/or reimbursed — class specific	$	619

	Institutional		Investor A		Investor C		Total
Transfer agent fees waived and/or reimbursed — class specific	$	11,687	$	26,501	$	103	$	38,291

The Manager and BRIL have also voluntarily agreed to waive a portion of their respective management, investment advisory and service and distribution fees and/or reimburse operating expenses to enable the Fund to maintain minimum levels of daily net investment income if applicable. These amounts, if any, are reported in the Statement of Operations as fees waived and/or reimbursed by the Manager, Distribution fees waived and/or reimbursed — class specific and transfer agent fees waived and/or reimbursed — class specific. The Manager and BRIL may discontinue the waiver and/or reimbursement at any time. For the six months ended October 31, 2021, the amounts waived and/or reimbursed were as follows:

	Institutional		Investor A		Investor C		Total
Transfer agent fees waived and/or reimbursed — class specific	$	3,310	$	32,582	$	139	$	36,031

	Investor C
Distribution fees waived and/or reimbursed — class specific	$	2,905
Fees waived and/or reimbursed by the Manager	$	740,585

Trustees and Officers: Certain trustees and/or officers of the Trust are directors and/or officers of BlackRock or its affiliates. The Fund reimburses the Manager for a portion of the compensation paid to the Trust’s Chief Compliance Officer, which is included in Trustees and Officer in the Statement of Operations.

6.   INCOME TAX INFORMATION

It is the Fund’s policy to comply with the requirements of the Internal Revenue Code of 1986, as amended, applicable to regulated investment companies, and to distribute substantially all of its taxable income to its shareholders. Therefore, no U.S. federal income tax provision is required.

The Fund files U.S. federal and various state and local tax returns. No income tax returns are currently under examination. The statute of limitations on the Fund’s U.S. federal tax returns generally remains open for a period of three fiscal years after they are filed. The statutes of limitations on the Fund’s state and local tax returns may remain open for an additional year depending upon the jurisdiction.

Management has analyzed tax laws and regulations and their application to the Fund as of October 31, 2021, inclusive of the open tax return years, and does not believe that there are any uncertain tax positions that require recognition of a tax liability in the Fund’s financial statements.

7.   PRINCIPAL RISKS

In the normal course of business, the Fund invests in securities or other instruments and may enter into certain transactions, and such activities subject the Fund to various risks, including among others, fluctuations in the market (market risk) or failure of an issuer to meet all of its obligations. The value of securities or other instruments may also be affected by various factors, including, without limitation: (i) the general economy; (ii) the overall market as well as local, regional or global political and/or social instability;

N O T E S  T O  F I N A N C I A L  S T A T E M E N T S 17

Notes to Financial Statements  (unaudited) (continued)

(iii) regulation, taxation or international tax treaties between various countries; or (iv) currency, interest rate and price fluctuations. Local, regional or global events such as war, acts of terrorism, the spread of infectious illness or other public health issues, recessions, or other events could have a significant impact on the Fund and its investments. The Fund’s prospectus provides details of the risks to which the Fund is subject.

Market Risk: An outbreak of respiratory disease caused by a novel coronavirus has developed into a global pandemic and has resulted in closing borders, quarantines, disruptions to supply chains and customer activity, as well as general concern and uncertainty. The impact of this pandemic, and other global health crises that may arise in the future, could affect the economies of many nations, individual companies and the market in general in ways that cannot necessarily be foreseen at the present time. This pandemic may result in substantial market volatility and may adversely impact the prices and liquidity of a fund’s investments. The duration of this pandemic and its effects cannot be determined with certainty.

Counterparty Credit Risk: The Fund may be exposed to counterparty credit risk, or the risk that an entity may fail to or be unable to perform on its commitments related to unsettled or open transactions, including making timely interest and/or principal payments or otherwise honoring its obligations. The Fund manages counterparty credit risk by entering into transactions only with counterparties that the Manager believes have the financial resources to honor their obligations and by monitoring the financial stability of those counterparties. Financial assets, which potentially expose the Fund to market, issuer and counterparty credit risks, consist principally of financial instruments and receivables due from counterparties. The extent of the Fund’s exposure to market, issuer and counterparty credit risks with respect to these financial assets is approximately their value recorded in the Statement of Assets and Liabilities, less any collateral held by the Fund.

Concentration Risk: A diversified portfolio, where this is appropriate and consistent with a fund’s objectives, minimizes the risk that a price change of a particular investment will have a material impact on the NAV of a fund. The investment concentrations within the Fund’s portfolio are disclosed in its Schedule of Investments.

LIBOR Transition Risk: The United Kingdom’s Financial Conduct Authority announced a phase out of the London Interbank Offered Rate (“LIBOR”). Although many LIBOR rates will be phased out by the end of 2021, a selection of widely used USD LIBOR rates will continue to be published through June 2023 in order to assist with the transition. The Fund may be exposed to financial instruments tied to LIBOR to determine payment obligations, financing terms, hedging strategies or investment value. The transition process away from LIBOR might lead to increased volatility and illiquidity in markets for, and reduce the effectiveness of new hedges placed against, instruments whose terms currently include LIBOR. The ultimate effect of the LIBOR transition process on the Fund is uncertain.

8.   CAPITAL SHARE TRANSACTIONS

The number of shares sold, reinvested and redeemed corresponds to the net proceeds from the sale of shares, reinvestment of all distributions and cost of shares redeemed, respectively, since shares are sold and redeemed at $1.00 per share.

Transactions in capital shares for each class were as follows:

	Six Months Ended 10/31/21			Year Ended 04/30/21
Institutional
Shares sold		15,786,988			54,042,310
Shares issued in reinvestment of distributions		2,865			32,037
Shares redeemed		(15,340,602	)		(64,060,673	)
		449,251			(9,986,326	)
Investor A
Shares sold		45,400,939			179,898,533
Shares issued in reinvestment of distributions		30,421			145,119
Shares redeemed		(64,951,309	)		(239,393,188	)
		(19,519,949	)		(59,349,536	)
Investor C
Shares sold		188,672			1,371,921
Shares issued in reinvestment of distributions		75			460
Shares redeemed		(528,750	)		(2,276,243	)
		(340,003	)		(903,862	)
		(19,410,701	)		(70,239,724	)

As of October 31, 2021, BlackRock Financial Management, Inc., an affiliate of the Fund, owned 50,000 Investor C Shares of the Fund.

9.   SUBSEQUENT EVENTS

Management has evaluated the impact of all subsequent events on the Fund through the date the financial statements were issued and has determined that there were no subsequent events requiring adjustment or additional disclosure in the financial statements.

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Disclosure of Investment Advisory Agreement

The Board of Trustees (the “Board,” the members of which are referred to as “Board Members”) of BlackRock Financial Institutions Series Trust (the “Trust”) met on April 7, 2021 (the “April Meeting”) and May 10-12, 2021 (the “May Meeting”) to consider the approval to continue the investment advisory agreement (the “Agreement”) between the Trust, on behalf of BlackRock Summit Cash Reserves Fund (the “Fund”), and BlackRock Advisors, LLC (the “Manager” or “BlackRock”), the Fund’s investment advisor.

The Approval Process

Consistent with the requirements of the Investment Company Act of 1940 (the “1940 Act”), the Board considers the approval of the continuation of the Agreement for the Fund on an annual basis. The Board members whom are not “interested persons” of the Trust, as defined in the 1940 Act, are considered independent Board members (the “Independent Board Members”). The Board’s consideration entailed a year-long deliberative process during which the Board and its committees assessed BlackRock’s various services to the Fund, including through the review of written materials and oral presentations, and the review of additional information provided in response to requests from the Independent Board Members. The Board had four quarterly meetings per year, each typically extending for two days, as well as additional ad hoc meetings and executive sessions throughout the year, as needed. The committees of the Board similarly met throughout the year. The Board also had a fifth one-day meeting to consider specific information surrounding the renewal of the Agreement. In particular, the Board assessed, among other things, the nature, extent and quality of the services provided to the Fund by BlackRock, BlackRock’s personnel and affiliates, including (as applicable): investment management services; accounting oversight; administrative and shareholder services; oversight of the Fund’s service providers; risk management and oversight; and legal, regulatory and compliance services. Throughout the year, including during the contract renewal process, the Independent Board Members were advised by independent legal counsel, and met with independent legal counsel in various executive sessions outside of the presence of BlackRock’s management.

During the year, the Board, acting directly and through its committees, considered information that was relevant to its annual consideration of the renewal of the Agreement, including the services and support provided by BlackRock to the Fund and its shareholders. BlackRock also furnished additional information to the Board in response to specific questions from the Board. Among the matters the Board considered were: (a) investment performance for one-year, three-year, five-year, and/or since inception periods, as applicable, against peer funds, relevant benchmarks, and other performance metrics, as applicable, as well as BlackRock senior management’s and portfolio managers’ analyses of the reasons for any outperformance or underperformance relative to its peers, benchmarks, and other performance metrics, as applicable; (b) fees, including advisory, administration, if applicable, and other amounts paid to BlackRock and its affiliates by the Fund for services; (c) Fund operating expenses and how BlackRock allocates expenses to the Fund; (d) the resources devoted to, risk oversight of, and compliance reports relating to, implementation of the Fund’s investment objective, policies and restrictions, and meeting regulatory requirements; (e) BlackRock’s and the Fund’s adherence to applicable compliance policies and procedures; (f) the nature, character and scope of non-investment management services provided by BlackRock and its affiliates and the estimated cost of such services, as available; (g) BlackRock’s and other service providers’ internal controls and risk and compliance oversight mechanisms; (h) BlackRock’s implementation of the proxy voting policies approved by the Board; (i) execution quality of portfolio transactions; (j) BlackRock’s implementation of the Fund’s valuation and liquidity procedures; (k) an analysis of management fees paid to BlackRock for products with similar investment mandates across the open-end fund, exchange-traded fund (“ETF”), closed-end fund, sub-advised mutual fund, separately managed account, collective investment trust, and institutional separate account product channels, as applicable, and the similarities and differences between these products and the services provided as compared to the Fund; (l) BlackRock’s compensation methodology for its investment professionals and the incentives and accountability it creates, along with investment professionals’ investments in the fund(s) they manage; and (m) periodic updates on BlackRock’s business.

Prior to and in preparation for the April Meeting, the Board received and reviewed materials specifically relating to the renewal of the Agreement. The Independent Board Members continuously engaged in a process with their independent legal counsel and BlackRock to review the nature and scope of the information provided to the Board to better assist its deliberations. The materials provided in connection with the April Meeting included, among other things: (a) information independently compiled and prepared by Broadridge Financial Solutions, Inc. (“Broadridge”), based on either a Lipper classification or Morningstar category, regarding the Fund’s fees and expenses as compared with a peer group of funds as determined by Broadridge (“Expense Peers”) and the investment performance of the Fund as compared with a peer group of funds (“Performance Peers”); (b) information on the composition of the Expense Peers and Performance Peers and a description of Broadridge’s methodology; (c) information on the estimated profits realized by BlackRock and its affiliates pursuant to the Agreement and a discussion of fall-out benefits to BlackRock and its affiliates; (d) a general analysis provided by BlackRock concerning investment management fees received in connection with other types of investment products, such as institutional accounts, sub-advised mutual funds, ETFs, closed-end funds, open-end funds, and separately managed accounts, under similar investment mandates, as well as the performance of such other products, as applicable; (e) a review of non-management fees; (f) the existence, impact and sharing of potential economies of scale, if any, with the Fund; (g) a summary of aggregate amounts paid by the Fund to BlackRock; (h) sales and redemption data regarding the Fund’s shares; and (i) various additional information requested by the Board as appropriate regarding BlackRock’s and the Fund’s operations.

At the April Meeting, the Board reviewed materials relating to its consideration of the Agreement. As a result of the discussions that occurred during the April Meeting, and as a culmination of the Board’s year-long deliberative process, the Board presented BlackRock with questions and requests for additional information. BlackRock responded to these questions and requests with additional written information in advance of the May Meeting.

At the May Meeting, the Board concluded its assessment of, among other things: (a) the nature, extent and quality of the services provided by BlackRock; (b) the investment performance of the Fund as compared to its Performance Peers and to other metrics, as applicable; (c) the advisory fee and the estimated cost of the services and estimated profits realized by BlackRock and its affiliates from their relationship with the Fund; (d) the Fund’s fees and expenses compared to its Expense Peers; (e) the existence and sharing of potential economies of scale; (f) any fall-out benefits to BlackRock and its affiliates as a result of BlackRock’s relationship with the Fund; and (g) other factors deemed relevant by the Board Members.

The Board also considered other matters it deemed important to the approval process, such as other payments made to BlackRock or its affiliates relating to securities lending and cash management, and BlackRock’s services related to the valuation and pricing of Fund portfolio holdings. The Board noted the willingness of BlackRock’s personnel to engage in open, candid discussions with the Board. The members of the Board gave attention to all of the information that was furnished, and each Board Member placed varying degrees of importance on the various pieces of information that were provided to them. The Board evaluated the information available to it on a fund-by-fund basis. The following paragraphs provide more information about some of the primary factors that were relevant to the Board’s decision. The Board Members did not identify any particular information, or any single factor as determinative, and each Board Member may have attributed different weights to the various items and factors considered.

DISCLOSURE   OF   INVESTMENT   ADVISORY   AGREEMENT 19

Disclosure of Investment Advisory Agreement  (continued)

A. Nature, Extent and Quality of the Services Provided by BlackRock

The Board, including the Independent Board Members, reviewed the nature, extent and quality of services provided by BlackRock, including the investment advisory services, and the resulting performance of the Fund. Throughout the year, the Board compared Fund performance to the performance of a comparable group of mutual funds, relevant benchmarks, and performance metrics, as applicable. The Board met with BlackRock’s senior management personnel responsible for investment activities, including the senior investment officers. The Board also reviewed the materials provided by the Fund’s portfolio management team discussing the Fund’s performance, investment strategies and outlook.

The Board considered, among other factors, with respect to BlackRock: the number, education and experience of investment personnel generally and the Fund’s portfolio management team; research capabilities; investments by portfolio managers in the funds they manage; portfolio trading capabilities; use of technology; commitment to compliance; credit analysis capabilities; risk analysis and oversight capabilities; and the approach to training and retaining portfolio managers and other research, advisory and management personnel. The Board also considered BlackRock’s overall risk management program, including the continued efforts of BlackRock and its affiliates to address cybersecurity risks and the role of BlackRock’s Risk & Quantitative Analysis Group. The Board engaged in a review of BlackRock’s compensation structure with respect to the Fund’s portfolio management team and BlackRock’s ability to attract and retain high-quality talent and create performance incentives.

In addition to investment advisory services, the Board considered the nature and quality of the administrative and other non-investment advisory services provided to the Fund. BlackRock and its affiliates provide the Fund with certain administrative, shareholder and other services (in addition to any such services provided to the Fund by third parties) and officers and other personnel as are necessary for the operations of the Fund. In particular, BlackRock and its affiliates provide the Fund with administrative services including, among others: (i) responsibility for disclosure documents, such as the prospectus, the summary prospectus (as applicable), the statement of additional information and periodic shareholder reports; (ii) oversight of daily accounting and pricing; (iii) responsibility for periodic filings with regulators; (iv) overseeing and coordinating the activities of third-party service providers including, among others, the Fund’s custodian, fund accountant, transfer agent, and auditor; (v) organizing Board meetings and preparing the materials for such Board meetings; (vi) providing legal and compliance support; (vii) furnishing analytical and other support to assist the Board in its consideration of strategic issues such as the merger, consolidation or repurposing of certain open-end funds; and (viii) performing or managing administrative functions necessary for the operation of the Fund, such as tax reporting, expense management, fulfilling regulatory filing requirements, overseeing the Fund’s distribution partners, and shareholder call center and other services. The Board reviewed the structure and duties of BlackRock’s fund administration, shareholder services, and legal and compliance departments and considered BlackRock’s policies and procedures for assuring compliance with applicable laws and regulations. The Board considered the operation of BlackRock’s business continuity plans, including in light of the ongoing COVID-19 pandemic.

B. The Investment Performance of the Fund and BlackRock

The Board, including the Independent Board Members, reviewed and considered the performance history of the Fund throughout the year and at the April Meeting. In preparation for the April Meeting, the Board was provided with reports independently prepared by Broadridge, which included an analysis of the Fund’s performance as of December 31, 2020, as compared to its Performance Peers. Broadridge ranks funds in quartiles, ranging from first to fourth, where first is the most desirable quartile position and fourth is the least desirable. In connection with its review, the Board received and reviewed information regarding the investment performance of the Fund as compared to its Performance Peers and a weighted average benchmark of similar funds, as defined by BlackRock (“Benchmark Weighted Average”). The Board and its Performance Oversight Committee regularly review and meet with Fund management to discuss the performance of the Fund throughout the year.

In evaluating performance, the Board focused particular attention on funds with less favorable performance records. The Board also noted that while it found the data provided by Broadridge generally useful, it recognized the limitations of such data, including in particular, that notable differences may exist between a fund and its Performance Peers (for example, the investment objectives and strategies). Further, the Board recognized that the performance data reflects a snapshot of a period as of a particular date and that selecting a different performance period could produce significantly different results. The Board also acknowledged that long-term performance could be impacted by even one period of significant outperformance or underperformance, and that a single investment theme could have the ability to disproportionately affect long-term performance.

The Board reviewed the Fund’s performance within the context of the low yield environment. In addition to reviewing the Fund’s performance and current yield, it also reviews the liquidity, duration, credit quality and other risk factors of the Fund’s portfolio. The Board noted that for each of the one- and three-year periods reported, the Fund underperformed its Benchmark Weighted Average. The Board noted that BlackRock believes that the Benchmark Weighted Average is an appropriate performance metric for the Fund, and that BlackRock has explained its rationale for this belief to the Board. The Board and BlackRock reviewed the Fund’s underperformance relative to its Benchmark Weighted Average during the applicable periods.

C. Consideration of the Advisory/Management Fees and the Estimated Cost of the Services and Estimated Profits Realized by BlackRock and its Affiliates from their Relationship with the Fund

The Board, including the Independent Board Members, reviewed the Fund’s contractual management fee rate compared with those of its Expense Peers. The contractual management fee rate represents a combination of the advisory fee and any administrative fees, before taking into account any reimbursements or fee waivers. The Board also compared the Fund’s total expense ratio, as well as its actual management fee rate, to those of its Expense Peers. The total expense ratio represents a fund’s total net operating expenses, including any 12b-1 or non-12b-1 service fees. The total expense ratio gives effect to any expense reimbursements or fee waivers, and the actual management fee rate gives effect to any management fee reimbursements or waivers. The Board considered the services provided and the fees charged by BlackRock and its affiliates to other types of clients with similar investment mandates, as applicable, including institutional accounts and sub-advised mutual funds (including mutual funds sponsored by third parties).

The Board received and reviewed statements relating to BlackRock’s financial condition. The Board reviewed BlackRock’s profitability methodology and was also provided with an estimated profitability analysis that detailed the revenues earned and the expenses incurred by BlackRock for services provided to the Fund. The Board reviewed BlackRock’s estimated profitability with respect to the Fund and other funds the Board currently oversees for the year ended December 31, 2020 compared to available aggregate estimated profitability data provided for the prior two years. The Board reviewed BlackRock’s estimated profitability with respect to certain other U.S. fund complexes

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Disclosure of Investment Advisory Agreement  (continued)

managed by the Manager and/or its affiliates. The Board reviewed BlackRock’s assumptions and methodology of allocating expenses in the estimated profitability analysis, noting the inherent limitations in allocating costs among various advisory products. The Board recognized that profitability may be affected by numerous factors including, among other things, fee waivers and expense reimbursements by the Manager, the types of funds managed, precision of expense allocations and business mix. The Board thus recognized that calculating and comparing profitability at the individual fund level is difficult.

The Board noted that, in general, individual fund or product line profitability of other advisors is not publicly available. The Board reviewed BlackRock’s overall operating margin, in general, compared to that of certain other publicly traded asset management firms. The Board considered the differences between BlackRock and these other firms, including the contribution of technology at BlackRock, BlackRock’s expense management, and the relative product mix.

The Board considered whether BlackRock has the financial resources necessary to attract and retain high quality investment management personnel to perform its obligations under the Agreement and to continue to provide the high quality of services that is expected by the Board. The Board further considered factors including but not limited to BlackRock’s commitment of time, assumption of risk, and liability profile in servicing the Fund, including in contrast to what is required of BlackRock with respect to other products with similar investment mandates across the open-end fund, ETF, closed-end fund, sub-advised mutual fund, separately managed account, collective investment trust, and institutional separate account product channels, as applicable.

The Board reviewed the expenses within the context of the low yield environment, and any consequent expense waivers and reimbursements necessary to maintain minimum levels of daily net investment income, as applicable. The Board noted that the Fund’s contractual management fee rate ranked in the fourth quartile, and that the actual management fee rate and total expense ratio ranked in the fourth and second quartiles, respectively, relative to the Fund’s Expense Peers. In addition, the Board noted that BlackRock and the Board agreed to a contractual expense cap on the Fund’s total expenses as a percentage of the Fund’s average daily net assets on a class-by-class basis.

D. Economies of Scale

The Board, including the Independent Board Members, considered the extent to which economies of scale might be realized as the assets of the Fund increase, including the existence of fee waivers and/or expense caps, as applicable, noting that any contractual fee waivers and contractual expense caps had been approved by the Board. In its consideration, the Board further considered the continuation and/or implementation of fee waivers and/or expense caps, as applicable. The Board also considered the extent to which the Fund benefits from such economies of scale in a variety of ways, and whether there should be changes in the advisory fee rate or breakpoint structure in order to enable the Fund to more fully participate in these economies of scale. The Board considered the Fund’s asset levels and whether the current fee schedule was appropriate.

E. Other Factors Deemed Relevant by the Board Members

The Board, including the Independent Board Members, also took into account other ancillary or “fall-out” benefits that BlackRock or its affiliates may derive from BlackRock’s respective relationships with the Fund, both tangible and intangible, such as BlackRock’s ability to leverage its investment professionals who manage other portfolios and its risk management personnel, an increase in BlackRock’s profile in the investment advisory community, and the engagement of BlackRock’s affiliates as service providers to the Fund, including for administrative, distribution, securities lending and cash management services. The Board also considered BlackRock’s overall operations and its efforts to expand the scale of, and improve the quality of, its operations. The Board also noted that, subject to applicable law, BlackRock may use and benefit from third-party research obtained by soft dollars generated by certain registered fund transactions to assist in managing all or a number of its other client accounts.

In connection with its consideration of the Agreement, the Board also received information regarding BlackRock’s brokerage and soft dollar practices. The Board received reports from BlackRock which included information on brokerage commissions and trade execution practices throughout the year.

Conclusion

The Board, including the Independent Board Members, unanimously approved the continuation of the Agreement between the Manager and the Trust, on behalf of the Fund, for a one-year term ending June 30, 2022. Based upon its evaluation of all of the aforementioned factors in their totality, as well as other information, the Board, including the Independent Board Members, was satisfied that the terms of the Agreement were fair and reasonable and in the best interest of the Fund and its shareholders. In arriving at its decision to approve the Agreement, the Board did not identify any single factor or group of factors as all-important or controlling, but considered all factors together, and different Board Members may have attributed different weights to the various factors considered. The Independent Board Members were also assisted by the advice of independent legal counsel in making this determination.

DISCLOSURE   OF   INVESTMENT   ADVISORY   AGREEMENT 21

Additional Information

General Information

Quarterly performance, semi-annual and annual reports, current net asset value and other information regarding the Fund may be found on BlackRock’s website, which can be accessed at blackrock.com. Any reference to BlackRock’s website in this report is intended to allow investors public access to information regarding the Fund and does not, and is not intended to, incorporate BlackRock’s website in this report.

Householding

The Fund will mail only one copy of shareholder documents, including prospectuses, annual and semi-annual reports, Rule 30e-3 notices and proxy statements, to shareholders with multiple accounts at the same address. This practice is commonly called “householding” and is intended to reduce expenses and eliminate duplicate mailings of shareholder documents. Mailings of your shareholder documents may be householded indefinitely unless you instruct us otherwise. If you do not want the mailing of these documents to be combined with those for other members of your household, please call the Transfer Agent at (800) 441-7762.

Availability of Quarterly Schedule of Investments

The Fund files its complete schedule of portfolio holdings with the SEC each month on Form N-MFP. The Fund’s reports on Form N-MFP are available on the SEC’s website at sec.gov. The Fund makes portfolio holdings available to shareholders on its website at blackrock.com.

Availability of Proxy Voting Policies, Procedures and Voting Records

A description of the policies and procedures that the Fund uses to determine how to vote proxies relating to portfolio securities and information about how the Fund voted proxies relating to securities held in the Fund’s portfolio during the most recent 12-month period ended June 30 is available without charge, upon request (1) by calling (800) 626-1960; (2) on the BlackRock website at blackrock.com; and (3) on the SEC’s website at sec.gov.

Shareholder Privileges

Account Information

Call us at (800) 441-7762 from 8:00 AM to 6:00 PM ET on any business day to get information about your account balances, recent transactions and share prices. You can also visit blackrock.com for more information.

Automatic Investment Plans

Investor class shareholders who want to invest regularly can arrange to have $50 or more automatically deducted from their checking or savings account and invested in any of the BlackRock funds.

Systematic Withdrawal Plans

Investor class shareholders can establish a systematic withdrawal plan and receive periodic payments of $50 or more from their BlackRock funds, as long as their account balance is at least $10,000.

Retirement Plans

Shareholders may make investments in conjunction with Traditional, Rollover, Roth, Coverdell, Simple IRAs, SEP IRAs and 403(b) Plans.

BlackRock Privacy Principles

BlackRock is committed to maintaining the privacy of its current and former fund investors and individual clients (collectively, “Clients”) and to safeguarding their non-public personal information. The following information is provided to help you understand what personal information BlackRock collects, how we protect that information and why in certain cases we share such information with select parties.

If you are located in a jurisdiction where specific laws, rules or regulations require BlackRock to provide you with additional or different privacy-related rights beyond what is set forth below, then BlackRock will comply with those specific laws, rules or regulations.

BlackRock obtains or verifies personal non-public information from and about you from different sources, including the following: (i) information we receive from you or, if applicable, your financial intermediary, on applications, forms or other documents; (ii) information about your transactions with us, our affiliates, or others; (iii) information we receive from a consumer reporting agency; and (iv) from visits to our websites.

BlackRock does not sell or disclose to non-affiliated third parties any non-public personal information about its Clients, except as permitted by law or as is necessary to respond to regulatory requests or to service Client accounts. These non-affiliated third parties are required to protect the confidentiality and security of this information and to use it only for its intended purpose.

We may share information with our affiliates to service your account or to provide you with information about other BlackRock products or services that may be of interest to you. In addition, BlackRock restricts access to non-public personal information about its Clients to those BlackRock employees with a legitimate business need for the

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Additional Information  (continued)

BlackRock Privacy Principles (continued)

information. BlackRock maintains physical, electronic and procedural safeguards that are designed to protect the non-public personal information of its Clients, including procedures relating to the proper storage and disposal of such information.

Fund and Service Providers

Investment Adviser	Independent Registered Public Accounting Firm
BlackRock Advisors, LLC	Deloitte & Touche LLP
Wilmington, DE 19809	Boston, MA 02116
Accounting Agent and Custodian	Legal Counsel
State Street Bank and Trust Company	Sidley Austin LLP
Boston, MA 02111	New York, NY 10019
Transfer Agent	Address of the Fund
BNY Mellon Investment Servicing (US) Inc.	100 Bellevue Parkway
Wilmington, DE 19809	Wilmington, DE 19809
Distributor
BlackRock Investments, LLC
New York, NY 10022

A D D I T I O N A L  I N F O R M A T I O N 23

Glossary of Terms Used in this Report

Portfolio Abbreviation

LIBOR	London Interbank Offered Rate
SOFR	Secured Overnight Financing Rate

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Want to know more?

blackrock.com | 800-441-7762

This report is intended for current holders. It is not authorized for use as an offer of sale or a solicitation of an offer to buy shares of the Fund unless preceded or accompanied by the Fund’s current prospectus. You could lose money by investing in the Fund. Although the Fund seeks to preserve the value of your investment at $1.00 per share, it cannot guarantee it will do so. An investment in the Fund is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. The Fund’s sponsor has no legal obligation to provide financial support to the Fund at any time. Performance data quoted represents past performance and does not guarantee future results. Total return information assumes reinvestment of all distributions. Current performance may be higher or lower than the performance data quoted. For current month-end performance information, call (800) 626-1960. The Fund’s current 7-day yield more closely reflects the current earnings of the Fund than the total returns quoted. Statements and other information herein are as dated and are subject to change.

SUMMITMM-10/21-SAR

(b) Not Applicable

Item 2 – Code of Ethics – Not Applicable to this semi-annual report

Item 3 – Audit Committee Financial Expert – Not Applicable to this semi-annual report

Item 4 – Principal Accountant Fees and Services – Not Applicable to this semi-annual report

Item 5 – Audit Committee of Listed Registrant – Not Applicable

Item 6 – Investments

(a) The registrant’s Schedule of Investments is included as part of the Report to Stockholders filed under Item 1(a) of this Form.

(b) Not Applicable due to no such divestments during the semi-annual period covered since the previous Form N-CSR filing.

Item 7 – Disclosure of Proxy Voting Policies and Procedures for Closed-End Management Investment Companies – Not Applicable

Item 8 – Portfolio Managers of Closed-End Management Investment Companies – Not Applicable

Item 9 – Purchases of Equity Securities by Closed-End Management Investment Company and Affiliated Purchasers – Not Applicable

Item 10 – Submission of Matters to a Vote of Security Holders –There have been no material changes to these procedures.

Item 11 – Controls and Procedures

(a) The registrant’s principal executive and principal financial officers, or persons performing similar functions, have concluded that the registrant’s disclosure controls and procedures (as defined in Rule 30a-3(c) under the Investment Company Act of 1940, as amended (the “1940 Act”)) are effective as of a date within 90 days of the filing of this report based on the evaluation of these controls and procedures required by Rule 30a-3(b) under the 1940 Act and Rule 15d-15(b) under the Securities Exchange Act of 1934, as amended.

(b) There were no changes in the registrant’s internal control over financial reporting (as defined in Rule 30a-3(d) under the 1940 Act) that occurred during the period covered by this report that have materially affected, or are reasonably likely to materially affect, the registrant’s internal control over financial reporting.

Item 12 – Disclosure of Securities Lending Activities for Closed-End Management Investment Companies – Not Applicable

Item 13 – Exhibits attached hereto

(a)(1) Code of Ethics – Not Applicable to this semi-annual report

(a)(2) Section 302 Certifications are attached

(a)(3) Any written solicitation to purchase securities under Rule 23c-1 – Not Applicable

(a)(4) Change in Registrant’s independent public accountant – Not Applicable

(b) Section 906 Certifications are attached

Pursuant to the requirements of the Securities Exchange Act of 1934 and the Investment Company Act of 1940, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

BlackRock Financial Institutions Series Trust

By:	/s/ John M. Perlowski
	John M. Perlowski
	Chief Executive Officer (principal executive officer) of
	BlackRock Financial Institutions Series Trust

Date: January 4, 2022

Pursuant to the requirements of the Securities Exchange Act of 1934 and the Investment Company Act of 1940, this report has been signed below by the following persons on behalf of the registrant and in the capacities and on the dates indicated.

By:	/s/ John M. Perlowski
	John M. Perlowski
	Chief Executive Officer (principal executive officer) of
	BlackRock Financial Institutions Series Trust

Date: January 4, 2022

By:	/s/ Trent Walker
	Trent Walker
	Chief Financial Officer (principal financial officer) of
	BlackRock Financial Institutions Series Trust

Date: January 4, 2022