📋 In This Guide
Why Verify a GSTIN Before Trusting It
Every business registered under India's Goods and Services Tax regime is issued a unique 15-character GSTIN (GST Identification Number). It appears on every tax invoice, e-way bill, and GST return — and it is the single most important field to get right when you record a purchase, claim Input Tax Credit, or onboard a new vendor.
A single mistyped character in a GSTIN can silently break Input Tax Credit reconciliation for the buyer, delay refunds, and trigger mismatch notices months later during GST return filing. Because the number is dense and easy to transpose, a fast, reliable way to catch typos before they reach an invoice is genuinely useful for accountants, freelancers, and small business owners across India.
State Code
First 2 digits identify the registered state or UT
PAN
Next 10 characters are the business's actual PAN
Entity Code
13th character counts registrations for that PAN in-state
Checksum
15th digit mathematically validates the whole number
How a GSTIN Is Structured — Digit by Digit
A GSTIN is always exactly 15 characters, and every position has a fixed meaning defined by the GST Council. Understanding this structure is what lets a computer — or a careful human — spot an obviously wrong number instantly.
Position 1–2 — State Code
A two-digit numeric code representing the state or union territory where the business applied for registration. This is the same code used on other GST documents and is fixed by the Census 2011 state code list, not the postal PIN code system.
Position 3–12 — Embedded PAN
The business's 10-character Income Tax PAN, unchanged. This is why a GSTIN can be cross-checked against a company's PAN — the middle section should match exactly.
Position 13 — Entity / Registration Number
Indicates how many GST registrations the same PAN holder has taken within that one state. Most businesses have a single registration per state, so this is usually "1".
Position 14 — Default Character "Z"
Currently always the letter Z, reserved by the GST department for possible future use. A GSTIN with anything other than Z in this position is invalid today.
Position 15 — Checksum Digit
A single alphanumeric character mathematically derived from the first 14 characters, used purely to detect data-entry errors.
How the GSTIN Checksum Digit Is Calculated
The checksum uses a well-documented method called the Luhn mod-36 algorithm — the same family of checksum used to catch typos in many identification numbers worldwide, adapted to GSTIN's 36-character alphabet (0–9 and A–Z).
GST State Codes — Full Reference Table
These two-digit codes appear as the first two characters of every GSTIN registered in that state or union territory.
| Code | State / UT | Code | State / UT |
|---|---|---|---|
| 01 | Jammu & Kashmir | 20 | Jharkhand |
| 02 | Himachal Pradesh | 21 | Odisha |
| 03 | Punjab | 22 | Chhattisgarh |
| 04 | Chandigarh | 23 | Madhya Pradesh |
| 05 | Uttarakhand | 24 | Gujarat |
| 06 | Haryana | 26 | Dadra & Nagar Haveli and Daman & Diu |
| 07 | Delhi | 27 | Maharashtra |
| 08 | Rajasthan | 29 | Karnataka |
| 09 | Uttar Pradesh | 30 | Goa |
| 10 | Bihar | 32 | Kerala |
| 11 | Sikkim | 33 | Tamil Nadu |
| 12 | Arunachal Pradesh | 34 | Puducherry |
| 13 | Nagaland | 35 | Andaman & Nicobar Islands |
| 14 | Manipur | 36 | Telangana |
| 15 | Mizoram | 37 | Andhra Pradesh |
| 16 | Tripura | 38 | Ladakh |
| 17 | Meghalaya | 97 | Other Territory |
| 18 | Assam | 99 | Centre Jurisdiction |
| 19 | West Bengal | — | — |
Entity / Registration Number Explained
The 13th character tracks multiple registrations under one PAN within a single state — common for large groups running several business verticals from the same state.
| 13th Character | Meaning |
|---|---|
| 1 – 9 | 1st to 9th GST registration for that PAN in the state |
| A | 10th registration for that PAN in the state |
| B – Z | 11th through 35th registration for that PAN in the state |
In practice, the overwhelming majority of GSTINs carry "1" here, since most businesses register only once per state.
GSTIN vs PAN — What's the Difference
PAN and GSTIN are related but serve different purposes. PAN is a lifetime identity number for tax purposes issued once to a person or company. GSTIN is a state-wise registration number under GST — a single PAN can have one GSTIN per state it operates in, so a company with warehouses in five states could legitimately hold five different GSTINs, all sharing the same embedded PAN.
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5 Common GSTIN Mistakes to Avoid
Frequently Asked Questions
GSTIN stands for Goods and Services Tax Identification Number — a unique 15-character alphanumeric code assigned to every business registered under GST in India. It is issued by the GST department and appears on every tax invoice, GST return, and e-way bill.
Enter the 15-character GSTIN into the validator above. It checks that the format matches the official pattern and verifies the checksum digit using the Luhn mod-36 algorithm — confirming the number is structurally valid. For live registration status, check the official GST portal.
The first 2 digits are the state code, the next 10 characters are the business's PAN, the 13th character is the entity registration number for that PAN in that state, the 14th is always Z, and the 15th is a checksum digit.
The 15th character is a check digit generated using the Luhn mod-36 algorithm applied to the first 14 characters, purely to catch typos — a single mistyped character will almost always produce a checksum mismatch.
No. This tool checks format and checksum validity only. It cannot confirm whether the GSTIN belongs to an active, registered taxpayer — for that, search it on the official GST portal at services.gst.gov.in.
PAN is a 10-character code issued by the Income Tax Department to identify a person or entity. GSTIN is a 15-character number that embeds the PAN plus a state code and registration details — one PAN holder can have multiple GSTINs across states.
The first two digits of every GSTIN represent the state or union territory of registration, using a fixed numeric code — for example 27 is Maharashtra, 07 is Delhi, and 29 is Karnataka. The full list is in the reference table above.
An invoice with an invalid or mistyped GSTIN can cause Input Tax Credit mismatches for your buyer during return reconciliation, delayed reimbursements, and possible notices from the GST department.
No. All validation and decoding happens instantly inside your browser using JavaScript. Nothing is uploaded, logged, or stored on any server.
The 13th character indicates how many GST registrations the same PAN holder has within that state — it runs 1–9 then A–Z, so a first registration gets 1, an eleventh gets A, and so on.