Free tool
GSTIN Validator & Decoder
Every GSTIN carries a check digit derived from the other fourteen characters. Paste one in and this verifies that maths instantly — then decodes the state, the PAN inside it, and what kind of entity it belongs to.
15 characters · nothing is sent to us or stored
What this proves, and what it doesn’t. A passing check digit means the number is well-formed. It does not mean the registration exists, is active, or belongs to who you think. For status and legal name, look the GSTIN up on the gst.gov.in portal.
How a GSTIN is built
Fifteen characters, and each block means something. Take
27AAPFU0939F1ZV:
| Position | Value | Meaning |
|---|---|---|
| 1–2 | 27 | State code — 27 is Maharashtra |
| 3–12 | AAPFU0939F | PAN of the registered entity |
| 13 | 1 | Number of registrations that PAN holds in that state |
| 14 | Z | Fixed default character |
| 15 | V | Check digit computed from positions 1–14 |
How the check digit works
Each of the first fourteen characters is converted to a value — 0–9 for digits, 10–35 for A–Z. Each value is multiplied by a weight that alternates between 1 and 2. For every product, you add together the quotient and the remainder when divided by 36. Sum all fourteen results, and the check digit is whatever value brings that sum up to the next multiple of 36.
The practical effect: a single mistyped character almost always breaks the checksum. That is why this catches transcription errors the moment a supplier’s invoice is entered, rather than at the point the input credit is rejected months later.
Where this matters in practice
- Vendor onboarding. Validate the GSTIN before the first purchase order, not after the first payment.
- Invoice entry. A wrong GSTIN on a purchase invoice means the credit will not match in GSTR-2B.
- Master data cleanups. Running every vendor GSTIN through a checksum usually turns up a handful of duplicates and typos in any ledger that has been going a few years.
The mismatches this catches are the same ones that surface in GSTR-2B reconciliation — just months earlier and far more cheaply. If reconciling credit every month is currently nobody’s job, that is what our GST and TDS service does.
GSTIN — common questions
How do I check if a GSTIN is valid?
A GSTIN carries a built-in check digit as its 15th character, calculated from the first 14. If the character doesn’t match the calculation, the number is wrong — mistyped or fabricated. This tool runs that calculation in your browser, so it catches a bad number instantly without any lookup.
What do the 15 characters of a GSTIN mean?
The first two digits are the state code. The next ten are the PAN of the business. The thirteenth is the entity number — how many registrations that PAN holds in that state. The fourteenth is ‘Z’ by default. The fifteenth is a checksum computed from the other fourteen.
Does a valid check digit mean the GSTIN is real and active?
No, and this is the important limit. The check digit proves the number is well-formed, not that it exists or is currently active. A structurally valid GSTIN could still be cancelled, suspended, or never issued. For status you must look it up on the GST portal.
Why does the PAN inside a GSTIN matter?
Because it ties the registration to a legal entity. If a supplier’s invoice shows a GSTIN whose embedded PAN doesn’t match the PAN they gave you elsewhere, something is wrong — a typo at best, and at worst an invoice from a different entity than you think you’re dealing with.
What is the fourth character of the PAN inside a GSTIN?
It encodes the entity type: C for company, P for individual, H for HUF, F for firm or LLP, T for trust, A for AOP, B for BOI, G for government, L for local authority, J for artificial juridical person. This tool decodes it for you.
Serving businesses across India
Catching typos is the cheap part.
The expensive part is input credit you claimed that your supplier never reported. We reconcile GSTR-2B against your purchase register every month, before the return goes out.
Delivered within 24 working hours, or next month is on us. 24 working hours from the moment we have your complete data. The clock runs Monday to Saturday and pauses on Sundays and public holidays. Terms