TAN

Validator and formatter for Indian Tax Deduction Account Numbers (TAN).

TAN is a 10-character alphanumeric code issued by the Indian Income Tax Department to entities required to deduct or collect tax at source (TDS/TCS). It is mandatory on all TDS/TCS returns, certificates, and challans. TANs are issued and administered under Section 203A of the Income Tax Act, 1961.

Format: [A-Z]{4}[0-9]{5}[A-Z] — 10 characters total

• Characters 1–4: jurisdiction code (uppercase letters, typically city/region abbreviation)

• Characters 5–9: five-digit sequential number assigned by the Income Tax Department

• Character 10: single uppercase letter (structural check character; no public algorithm exists)

No checksum: The Income Tax Department does not publish a checksum algorithm for TAN. Validation is structural (format) only.

No mask(): TAN is a public business identifier — entities publish their TAN on invoices and tax certificates. No masking is required or provided per KotIndia PII policy (§3.5).

Accepted input forms (all normalised before validation):

• Raw uppercase: "MUMD12345A"

• Lowercase: "mumd12345a" — normalised to uppercase

• Mixed case: "MumD12345a" — normalised to uppercase

• With spaces: "MUMD 12345 A" — internal whitespace stripped

• Whitespace padded: " MUMD12345A " — leading/trailing whitespace trimmed

This object is stateless and thread-safe.

Samples

TAN.validate("PDES03028F") // ValidationResult.Valid
TAN.format("pdes03028f") // "PDES03028F"