Glossary · Audit
UDIN
Also known as: Unique Document Identification Number
UDIN, or Unique Document Identification Number, is an 18-digit number generated from the ICAI portal to authenticate documents certified by a practising Chartered Accountant. It lets anyone verify that a certificate, report or attestation was genuinely issued by the CA who signed it.
A Unique Document Identification Number (UDIN) is the 18-digit code a practising Chartered Accountant generates on the ICAI UDIN portal to authenticate any document they certify or attest. ICAI brought it in to stop forged certificates issued in the name of genuine members.
Why UDIN matters for every CA certificate
When a CA signs a certificate, audit report or attestation, a UDIN is generated against that document on the ICAI portal. Any third party — a bank, a regulator, a client — can then verify the UDIN online and confirm the document is genuine and was issued by that specific member.
In practice this means:
- Each certified document gets its own UDIN
- The CA records key details of the document when generating it
- Regulators increasingly require the UDIN to be quoted on filings
For audit work, UDIN generation is a standard step. A tax audit report must carry a valid UDIN, as must most certificates a bank or regulator asks for. The UDIN sits alongside the DSC the CA uses to sign filings on the portals — one authenticates the document, the other signs it.
The real headache for a firm is volume. During September and October, when tax audits pile up, every certifiable document needs its UDIN generated and quoted correctly, and a single missed entry can stall a client’s filing. Some practice management software keeps a UDIN register against client work so none slips through.
See how tools handle certification tracking in our rankings and our QwikCA review, and explore related audit terms in the glossary.