How Many Digits in a GST Number? (15 Characters)

A GST number has 15 characters — not digits, since it mixes letters and numbers. That single fact resolves most of the confusion people run into, because a few other, shorter identifiers (an 11-digit TIN, a 10-character PAN) get mixed up with it in everyday conversation.

The direct answer: 15 characters

A GST number, formally called a GSTIN (GST Identification Number), is always 15 characters long. It follows a fixed layout: 2 characters for the state code, 10 characters for the taxpayer's PAN, 1 character for a registration counter, 1 fixed character, and 1 checksum character at the end. Every valid GSTIN in India — for a company, an individual, a trust, or any other registered entity — is 15 characters, no more and no fewer.

However the question is phrased — how many digits in a GST number, how many digit of GST number, GST number how many digit — the answer is the same number, 15, and the only correction worth making is that they are characters rather than digits.

What each of the 15 characters holds

The length is not arbitrary: every position is doing something specific, and seeing all fifteen at once is usually faster than reading a description of them. Take 27AAACR5055K1Z7.

Position	Value	Always	What it is
1–2	27	Digits	State code — 27 is Maharashtra
3–7	AAACR	Letters	First five characters of the PAN
8–11	5055	Digits	The four numeric characters of the PAN
12	K	Letter	The PAN's final check letter
13	1	Digit or letter	Counts registrations held by this PAN in this state
14	Z	Always Z	Reserved for future use
15	7	Digit or letter	Checksum computed from the first 14 characters

Every position in a 15-character GSTIN, using 27AAACR5055K1Z7 as the example.

Positions 3 to 12 together are the taxpayer's complete 10-character PAN, lifted into the GSTIN unchanged. That is why 15 and not some other number: 2 + 10 + 3. We go through the checksum algorithm and the entity-type letter in detail in GSTIN format, character by character, and the relationship between the embedded PAN and a standalone PAN card in GST number vs PAN.

Why "digits" is slightly the wrong word

People say "15-digit GST number" constantly, and it is close enough to be understood, but it is not strictly accurate. A digit is a numeral, 0 through 9. A GSTIN mixes numerals with uppercase letters — for example 27AAACR5055K1Z7 contains far more letters than numbers. The more precise word is "character": a GSTIN is a 15-character alphanumeric code. This matters practically too — if you are writing validation logic, a regex that only accepts digits will reject every real GSTIN.

The identifiers people confuse it with

Three other identifiers get tangled up with GSTIN length, usually because they are also government registration numbers tied to a business or an individual.

Identifier	Length	What it is
PAN	10 characters	Income Tax Permanent Account Number, issued to individuals and entities
TAN	10 characters	Tax Deduction and Collection Account Number, for entities deducting TDS or collecting TCS
TIN (VAT era)	11 digits	Pre-GST state VAT registration number, discontinued when GST launched
CIN	21 characters	Corporate Identity Number from the Ministry of Corporate Affairs — company incorporation, nothing to do with GST
GSTIN / "GST number"	15 characters	Current GST registration number; the only one in this table that is a GST identifier at all

Identifiers commonly confused with the GST number.

"GST number" and "GSTIN" are not two different things with two different lengths — they are two names for the exact same 15-character code.

What a 10, 11 or 16-character "GST number" actually is

When a number that is called a GST number comes back the wrong length, it is almost always a different identifier rather than a corrupted GSTIN. The length itself usually tells you which one.

10 characters — a PAN or a TAN. If it is five letters, four digits, one letter, it is a PAN, and it is the PAN that would sit inside the GSTIN if one exists.
11 digits — almost certainly a pre-GST VAT-era TIN, carried forward in an old master record. It cannot be used for GST purposes.
14 characters — usually a GSTIN with a character dropped in transcription. Count the blocks: the missing one is normally a state-code digit or a PAN character.
16 or more characters — generally a GSTIN with trailing whitespace, a stray punctuation mark, or an e-invoice or ARN reference pasted in by mistake. Strip spaces and re-count before rejecting it.

For state codes specifically — the first two characters, and the only part that varies by where a business registered — see the full GST state code list.

How to spot an invalid GST number by length alone

Length is the fastest, cheapest check you can run on a GSTIN before doing anything else with it. If a string a customer or vendor gives you is shorter or longer than 15 characters, it cannot be a real GSTIN — no live lookup is even necessary to reject it. That said, correct length (and even a correct checksum) only proves the string is well-formed; it does not prove the GSTIN was ever issued or that the business is currently active. Confirming that requires checking it against live government records through something like our GST verification API, or the free GST number search tool for occasional lookups. If a real, correctly formatted GSTIN comes back with an unexpected status, see what a suspended GSTIN status means for what to do next.

Frequently asked questions

A GST number (GSTIN) has 15 characters in total. It is not purely numeric — it mixes digits and letters — so "digits" is a loose way of saying "characters".

Yes. "GST number" is the informal, everyday name people use; GSTIN (GST Identification Number) is the official term. They refer to the exact same 15-character code.

No. A PAN is 10 characters. A GSTIN is 15 characters and actually contains the full 10-character PAN inside it, at positions 3 through 12.

That was the TIN (Taxpayer Identification Number) used under the pre-GST VAT regime. It was replaced by the 15-character GSTIN when GST was introduced, and TINs are not valid for GST purposes.

Yes. Any string that is not exactly 15 characters, in the correct state-code + PAN + entity-code + Z + checksum layout, fails basic format validation and cannot be a real GSTIN.

Six positions are always numeric: the two state-code digits at the start, and the four digits inside the embedded PAN at positions 8 to 11. Five positions are always letters — positions 3 to 7 and position 12, all part of the PAN — and position 14 is always the letter Z. Positions 13 and 15 can be either a digit or a letter.

Yes. The 15-character layout is identical across every state and union territory in India. Only the first two characters change, and they identify the state of registration. There is no state with a longer or shorter GSTIN.

A note on accuracy. GST rules change often. This article reflects our understanding as of 14 October 2026 and is general information, not tax or legal advice. For the authoritative position, check gst.gov.in and cbic-gst.gov.in, or speak to a qualified tax professional about your specific situation.

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