| Cover Page | 12 Months Ended |
| Jun. 30, 2021shares | |
| Document Information [Line Items] | |
| Document Type | 20-F/A |
| Amendment Flag | true |
| Document Period End Date | Jun. 30, 2021 |
| Document Fiscal Year Focus | 2021 |
| Document Fiscal Period Focus | FY |
| Entity Registrant Name | Renalytix plc |
| Entity Central Index Key | 0001811115 |
| Current Fiscal Year End Date | --06-30 |
| Entity Well-known Seasoned Issuer | No |
| Entity Current Reporting Status | Yes |
| Entity Filer Category | Non-accelerated Filer |
| Entity Voluntary Filers | No |
| Entity Shell Company | false |
| Entity Emerging Growth Company | true |
| Entity Ex Transition Period | false |
| Entity Interactive Data Current | Yes |
| Entity Common Stock, Shares Outstanding | 72,197,286 |
| Document Accounting Standard | U.S. GAAP |
| Entity Address, Address Line One | Finsgate 5-7 Cranwood Street |
| Entity Address, City or Town | London |
| Entity Address, Postal Zip Code | EC1V 9EE |
| Entity Address, Country | GB |
| Document Annual Report | true |
| Document Transition Report | false |
| Entity File Number | 001-39387 |
| Document Shell Company Report | false |
| Document Registration Statement | false |
| No Trading Symbol Flag | true |
| Title of 12(b) Security | Ordinary shares, nominal value £0.0025 per share |
| Security Exchange Name | NASDAQ |
| Entity Incorporation, State or Country Code | X0 |
| Amendment Description | EXPLANATORY NOTE Renalytix plc (the “Company”) is filing this Amendment No. 1 (the “Amendment”) on Form 20-F/A to amend its Annual Report on Form 20-F for the fiscal year ended June 30, 2021, filed with the Securities and Exchange Commission on October 21, 2021 (the “Original 20-F”), for the purpose of filing revised versions of Exhibits 12.1 and 12.2 filed with the Original 20-F. The Company is filing revised exhibits solely in order to include in the certifications set forth in the Exhibits the reference to internal control over financial reporting in the introductory language to paragraph 4, which language was inadvertently omitted from the certifications when originally filed. The Amendment does not reflect events occurring after the date of the filing of the Original 20-F or modify or update any of the other disclosures contained therein in any way. Accordingly, the Amendment should be read in conjunction with the Original 20-F. The Amendment consists solely of the preceding cover page, this explanatory note, the signature page and paragraphs 1, 2, 4 and 5 of each of the revised certifications filed as exhibits to the Amendment. Because no financial statements have been included in this Amendment, paragraph 3 of each of the certifications set forth in the Exhibits has been omitted. |
| ICFR Auditor Attestation Flag | false |
| Business Contact [Member] | |
| Document Information [Line Items] | |
| Entity Address, Address Line One | Finsgate 5-7 Cranwood Street |
| Entity Address, City or Town | London |
| Entity Address, Postal Zip Code | EC1V 9EE |
| Entity Address, Country | GB |
| Contact Personnel Name | James McCullough Chief Executive Officer |
| City Area Code | 20 |
| Local Phone Number | 3139 2910 |
| American Depositary Shares [Member] | |
| Document Information [Line Items] | |
| Trading Symbol | RNLX |
| Title of 12(b) Security | American Depositary Shares, each representing two ordinary shares, nominal value £0.0025 per share |
| Security Exchange Name | NASDAQ |
