UDIN is an 18-character, system-generated number that ICAI requires a practising Chartered Accountant to generate for every certificate, report or attest document they sign. Third parties such as banks and regulators can check it on the UDIN portal to confirm the document was really issued by that CA.
Facts checked: 9 October 2026, against ICAI's FAQs on UDIN (4th edition, last updated 2 July 2024). Confirm the latest position on udin.icai.org before you rely on any date or time limit below.
Why ICAI introduced it
ICAI's own FAQ gives the reason plainly: financial documents were being certified by people misrepresenting themselves as CAs, and members were complaining about forged signatures. UDIN lets a bank, regulator or other recipient check that the document is genuine instead of trusting a signature and stamp.
Which documents need a UDIN
The ICAI Council (379th meeting, 17-18 December 2018) made UDIN mandatory in phases for full-time practising CAs.
| Document type | Mandatory from |
|---|---|
| All certificates | 1 February 2019 |
| GST and tax audit reports | 1 April 2019 |
| All other audit, assurance and attestation functions | 1 July 2019 |
All three dates have long since passed, so treat UDIN as a standing requirement. The FAQ lists many certificate types in the portal drop-down, including net worth (capital contribution) and Form 15CB certificates. If yours is not listed, the portal lets you choose "Others" and describe it. A UDIN is not required on a Peer Review Report.
The 18-character structure
| Part | Length | Meaning |
|---|---|---|
| YY | 2 | Last two digits of the year of generation |
| MMMMMM | 6 | The signing CA's ICAI membership number |
| Remaining | 10 | Alphanumeric, generated randomly by the system |
Because the middle block is the membership number, a UDIN is tied to one named member. Two partners who both sign the same document each generate their own.
Who can generate it
Only a CA with a full-time Certificate of Practice can register and generate. A firm cannot register; the signing partner or proprietor does it, and one UDIN is needed per assignment per signatory. When you generate it you select the firm's registration number (FRN), or state individual capacity.
What happens if you skip it
ICAI states that not generating a UDIN for a mandatory document is non-adherence to a Council decision and may attract disciplinary proceedings under the Second Schedule, Part II of the Chartered Accountants Act, 1949. Regulators and lenders may also simply refuse a document that carries no UDIN.
Worked scenario
A firm with two partners issues a net worth certificate for a loan applicant. Partner A signs it on 3 October. Partner A (not the firm, and not Partner B) logs in, selects the firm's FRN, picks the certificate type, enters the signing date and a short description, and generates the UDIN. It is then printed after the signature and membership number on the certificate. If the bank later verifies it, Partner A receives an email and SMS alert about the check.
A net worth certificate format and a UDIN register keep the number and the file together.
Where firms slip
- Treating UDIN as a firm-level number when it is personal to the signing member.
- Signing first and leaving UDIN generation for later with no tracking, then missing the time limit.
- Quoting the UDIN in the document but never recording it against the working papers.
Read next: how to generate a UDIN step by step and how to verify a UDIN.
Frequently asked questions
Is UDIN the same as a membership number?
No. The membership number is one part of it. The full UDIN is unique to each document and each signatory.
Does a certificate need a UDIN if the client did not ask for one?
If it falls within the mandated categories, yes. The requirement comes from ICAI, not the recipient.
Is there a fee for UDIN?
We could not confirm any fee from the ICAI FAQ, and none is mentioned there. Check the portal.
Read the audit glossary for related terms.
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