GST Number Validator
Finance & Indian IDsCheck if a GST number follows the correct 15-character format — state code, PAN, entity code, and checksum. Runs in your browser, no signup needed.
What is a GST?
A GST Number Validator checks whether a GSTIN (Goods and Services Tax Identification Number) conforms to the official 15-character format defined by the Goods and Services Tax Network (GSTN). GST was introduced in India on 1 July 2017 as a unified indirect tax, replacing a patchwork of central and state levies including VAT, service tax, and excise duty. Every business that registers under GST — mandatory above the prescribed turnover threshold — receives a unique GSTIN that identifies the taxpayer, their state, and their PAN.
A GSTIN is not a random identifier: each of its 15 characters carries specific meaning. The first two digits encode the state code (01–37), the next ten characters are the taxpayer's PAN number, the thirteenth character is an entity number for businesses with multiple registrations in one state, the fourteenth is always the letter Z, and the fifteenth is an alphanumeric checksum. A single character in the wrong position or character class makes the entire number invalid.
This validator checks the format of the GSTIN instantly as you type. It also breaks down each segment — telling you the state the number corresponds to, the embedded PAN portion, and the entity and checksum characters — so you can spot exactly where a typo occurred.
Important: format validation confirms the structure is correct; it does not verify that the GSTIN is currently registered, active, or in good standing with the GSTN portal. For live registration lookup, use the official GST portal. For related Indian financial ID validation, see the PAN Validator.
How to use this GST calculator
- Open the GST Number Validator on this page.
- Type or paste the GSTIN into the GST Number field. The validator automatically converts lowercase letters to uppercase, so you do not need to manually capitalise.
- The result badge updates instantly. A green Valid badge confirms the GSTIN matches the correct 15-character format.
- If the badge shows Invalid, read the error message — it specifies whether the length is wrong, the state code is out of range, or a specific segment has the wrong character pattern.
- Fix the character that is causing the failure — common issues are a digit where a letter is expected in the PAN portion, a wrong state code, or a missing character — and the badge updates immediately.
- For a valid GSTIN, review the segment breakdown in the details section to confirm the state code and embedded PAN match what you expect.
Formula & Methodology
The validator applies the official GSTN format rule using a regular expression:/^[0-9]{2}[A-Z]{5}[0-9]{4}[A-Z]{1}[1-9A-Z]{1}Z[0-9A-Z]{1}$/| Position | Characters | Rule | |---|---|---| | 1–2 | State code | Two digits, 01–37 | | 3–7 | PAN letters | Five uppercase letters (A–Z) | | 8–11 | PAN digits | Four digits (0–9) | | 12 | PAN check letter | One uppercase letter (A–Z) | | 13 | Entity number | One character: 1–9 or A–Z | | 14 | Fixed | Must be Z | | 15 | Checksum | One alphanumeric character (0–9 or A–Z) | Valid example:29ABCDE1234F1Z5State: 29 (Karnataka) | PAN: ABCDE1234F | Entity: 1 | Fixed: Z | Checksum: 5 Invalid example:99ABCDE1234F1Z5State code99is outside the valid range of 01–37, making the GSTIN invalid. The check is synchronous and purely client-side — no external API calls are made. The state name lookup uses a static map of Indian state codes defined in GST rules.