## UDIN — Unique Document Identification Number

### What is UDIN?

UDIN is an 18-digit alphanumeric, system-generated unique code that appears below the auditor's signature and membership number in an audit report or certificate.

### Purpose and Background

The ICAI introduced UDIN to address a specific malpractice:

Financial documents and certificates were being attested by non-CAs misrepresenting themselves as CA members
Signatures of CA members were being forged by non-CAs
Authorities and stakeholders were being misled

UDIN creates a verifiable trail: any stakeholder can check the UDIN portal to confirm that the document was genuinely signed by the CA whose name and membership number appear on it.

### How It Works

1. Only Chartered Accountants with a full-time Certificate of Practice (CoP) can register on the UDIN portal

2. The CA generates a UDIN by registering the document (audit report or certificate) on the portal

3. The UDIN is then mentioned in the audit report or certificate alongside the membership number

### Scope — Audit Reports AND Certificates

UDIN is not limited to audit reports. It is required for:

Audit reports signed by the CA
Certificates issued by the CA

> It is NOT required for general letters, management letters, or informal communications.

Worked example

### Example 1

Kiran's observation: Kiran notices an 18-character alphanumeric code at the bottom of an audit report, below the auditor's name and membership number. She correctly identifies this as a UDIN — a system-generated unique number from the ICAI UDIN portal that confirms the audit report was genuinely signed and registered by the named CA member.

### Example 2

Verification use case: A bank receives financial statements certified by a CA for a loan application. The credit officer enters the UDIN from the certificate into the ICAI portal. If the UDIN is valid and matches the CA's membership number and document details, the certificate is authentic. If the UDIN is not found or mismatched, it indicates potential forgery.

⚠️ Common exam mistakes

Thinking UDIN is required only for audit reports — it is also required for certificates issued by CAs.
Confusing the UDIN with the CA's membership number — the UDIN is a separate, document-specific, system-generated code.
Assuming any CA can generate a UDIN — only CAs with a full-time Certificate of Practice can register on and use the UDIN portal.

Reference: — ICAI UDIN Guidelines

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UDIN – Unique Document Identification Number

Worked example

⚠️ Common exam mistakes