Frequently asked
How do I read a GST number?
Break it into 5 parts: 2-digit state code, 10-character PAN, 1-digit entity number, the fixed letter Z, and a 1-character check digit.
Why show the check-digit math?
Most GST tools just say "valid" or "invalid" without showing why. We think a data reference site should show its work — the same way a calculator shows the calculation, not just the result.
Does this tool verify if a GST number is actually registered?
No. This decodes the structure and format only. For live registration status, use the official GST portal linked above.
What is a GSTIN and why does every registered business need one?
GSTIN (Goods and Services Tax Identification Number) is the unique 15-character registration number issued to every business registered under India's GST regime. It replaced the older, fragmented state-level VAT/TIN system with one PAN-linked number used for every GST filing, invoice, and input tax credit claim.
Can a single business have more than one GSTIN?
Yes. A business operating in multiple states needs a separate GSTIN for each state, since GST registration is state-specific. A business can also hold multiple GSTINs within one state for different verticals if it opts for separate registrations per business vertical.
Is GSTIN the same as a Tax Identification Number (TIN)?
No. TIN was the old state-level VAT registration number, discontinued when GST was introduced in July 2017. GSTIN is its nationwide replacement and is structurally different — it embeds the taxpayer's PAN, which TIN never did.
What happens if I enter an invalid GSTIN into this decoder?
The tool checks the format against the official 15-character pattern first. If the pattern doesn't match, or if the computed check digit doesn't equal the 15th character, it flags this clearly rather than pretending the number is valid.
Why does the GSTIN always end differently even for the same PAN?
Characters 13 and 15 vary based on registration count and the check-digit calculation, so two GSTINs sharing the same PAN and state will still differ in their final characters if the entity number changes.
Is quoting a GSTIN on an invoice mandatory?
Yes, for any registered supplier issuing a tax invoice. Missing or incorrect GSTIN on an invoice can block the recipient's input tax credit claim, which is why decoding and double-checking a GSTIN before filing is common practice.
What's the difference between GSTIN and UIN?
UIN (Unique Identification Number) is a separate class of registration for specific entities like foreign diplomatic missions and UN bodies, allowing them to claim GST refunds without acting as regular taxable persons. It follows a different format from a standard GSTIN.
Can I use this decoder for composition scheme taxpayers?
Yes — GSTINs issued under the composition scheme follow the same 15-character structure as regular GSTINs. The scheme affects how a business files returns and pays tax, not the format of its identification number.
Why does the 14th character in a GSTIN never change?
The 14th character is fixed as the letter "Z" by design, reserved by GSTN for potential future use. Every valid GSTIN in circulation today has "Z" in this position — if it's anything else, the number is not correctly formed.
How often should I re-verify a supplier's GSTIN?
Structural validation (what this tool does) only needs checking once, since the format itself doesn't change. Live registration status can change if a supplier's registration is cancelled or suspended, so businesses typically re-check active status periodically via the official portal, especially before large transactions.
Does the state code in a GSTIN ever change for an existing business?
No. The state code reflects where that specific GST registration was granted and stays fixed for that GSTIN's lifetime. If a business relocates its principal place of business to another state, it typically needs a new registration and a new GSTIN for that state.
What is the significance of the embedded PAN inside a GSTIN?
Embedding the PAN directly into the GSTIN links every GST registration back to a single income-tax identity, making it straightforward for tax authorities to cross-reference GST filings against income tax records for the same entity.
Can individuals without a business have a GSTIN?
Generally no — GST registration is tied to carrying out a taxable supply of goods or services above the prescribed turnover threshold, or voluntary registration for business purposes. A private individual with no business activity does not need or typically hold a GSTIN.
Why do some GSTINs start with "37" while businesses say they are in Andhra Pradesh?
State code 37 correctly maps to Andhra Pradesh in the current GST state code table; the older code 28 was used briefly during the reorganisation period before Telangana's formal separation and is now largely historical.
Is this GST decoder free to use for unlimited lookups?
Yes. It runs entirely as client-side logic in your browser with no query limits, no login, and no cost, since it performs local computation rather than calling any paid API or database.
About this GST decoder
This GST number decoder and GSTIN checker breaks down any GST registration number into its state code, embedded PAN, entity number, and check digit — with the full verification math shown, not hidden. Use it to decode a GSTIN, verify GST number format before invoicing, identify a business's registered state from its GST number, or understand the complete GST state code list across all 36 states and union territories.