GSTIN Checker — Validate a GST Number Instantly

Quick answer

A GSTIN is valid in format when it has exactly 15 characters: a 2-digit state code, the holder's 10-character PAN, one entity number, one letter (usually Z) and a check character. The last character is calculated from the first 14 by a fixed formula, so a single typing error almost always breaks it. This checker tests all of that instantly. To confirm the business name and active status, search the GSTIN on the GST portal.

How to use this GSTIN checker

The tool has a single field. Type or paste the 15-character GST number from an invoice, a quotation, a vendor form or a website, and the result appears straight away.

1. Enter the GSTIN. Lower-case letters are converted to capitals and spaces are removed automatically, so you can paste a number even if it was copied with gaps.
2. Read the verdict. You will see either "Valid GSTIN format" or a specific reason it is not valid.
3. Check the details. For a valid number, the tool shows the state, the PAN inside it, the type of taxpayer (based on the PAN), the registration number for that PAN in the state, and the check digit with a tick.
4. Confirm on the portal. For any supplier you are going to pay or claim credit from, search the same number on the official GST portal to see the legal name and whether the registration is active.

The checker runs entirely in your browser. Nothing you type is sent anywhere, which is why it works even offline — and also why it cannot tell you the business name or status, which only the government database holds.

What the checker tests, step by step

The tool runs four tests in a fixed order and stops at the first one that fails. Knowing the order helps you understand the message you see.

If all four pass, the number is a genuine-looking GSTIN. Note that the entity character (13th) cannot be 0 — a registration number starts from 1.

The structure of a GSTIN explained

Every regular GSTIN follows the same layout. Take the sample number 07ABCPK1234L1ZU (a made-up number used only for illustration).

The PAN part and the taxpayer type

Because the PAN is embedded inside the GSTIN, the checker can read the type of holder from the PAN's fourth character (the 6th character of the GSTIN). This is the same letter that tells the income tax department what kind of taxpayer a PAN belongs to.

This is a useful sense check. If a supplier's invoice says "XYZ Private Limited" but the GSTIN's PAN shows P (individual), the GSTIN probably belongs to someone else, or the company is billing under a proprietor's registration. Either way, ask before you pay.

The 13th character: more than one registration

One PAN can hold more than one GSTIN in the same state — for example, a business with separate registrations for different business verticals or places. The 13th character counts these: 1 for the first, 2 for the second, and so on, moving to letters after 9. A number like 09AAFFG4321H2ZK is the second registration of that PAN in Uttar Pradesh.

The 14th character

For regular taxpayers this is Z by default. The checker accepts any letter or digit here, because the format allows it, but if you see anything other than Z on an ordinary supplier's GSTIN, it is worth a second look on the portal.

How the check digit is calculated

The 15th character is not random. It is worked out from the first 14 characters using a standard checksum, and this is what lets the tool catch most typing mistakes without any internet connection.

The method works like this:

1. Give every character a value: digits 0–9 keep their value, and letters A–Z become 10–35 (A = 10, B = 11 … Z = 35).
2. Multiply the value of characters in odd positions (1st, 3rd, 5th…) by 1 and characters in even positions (2nd, 4th, 6th…) by 2.
3. For each product, divide by 36 and add the quotient and the remainder together.
4. Add up all 14 results.
5. Take the total's remainder when divided by 36, and subtract it from 36. If the answer is 36, use 0.
6. Convert the answer back to a character using the same table (0–9 as digits, 10–35 as A–Z). That is the check character.

Worked example: 07ABCPK1234L1Z?

The total is 150. 150 ÷ 36 leaves a remainder of 6. 36 − 6 = 30, and 30 corresponds to the letter U. So the full GSTIN is 07ABCPK1234L1ZU. Type it into the checker and you will see the tick.

Why this catches typing errors

Because every position has a weight, changing any single character changes the total, and so changes the expected check character. Swapping two neighbouring characters is caught too in most cases. For example, 09AAFFG4321H2ZK passes, but if someone types 09AAFFG4312H2ZK (with 21 swapped to 12), the checker reports that the last character should be L. That tells you at once that a digit was mistyped.

GST state codes

The first two digits tell you the state or union territory where the GSTIN is registered. The checker recognises these codes:

Codes 25 (old Daman & Diu) and 28 (old Andhra Pradesh) are also recognised, as some older registrations still carry them. Andhra Pradesh registrations now use 37.

Why the state code matters for tax

The state code on your supplier's GSTIN, compared with your own, is a quick indicator of whether the invoice should show CGST + SGST or IGST. If your GSTIN starts with 09 (Uttar Pradesh) and your supplier's starts with 07 (Delhi), a delivery of goods to you in Uttar Pradesh will normally carry IGST. The actual rule is based on the place of supply, but a mismatch between the state code and the tax heads on an invoice is a good reason to ask questions. You can work out the right split with our GST calculator.

Format valid vs registration active: the difference

This is the most important point on this page. A "Valid GSTIN format" result means the number is built correctly. It does not mean:

• the GSTIN has actually been issued to anyone;
• it belongs to the business named on the invoice;
• the registration is active today (it may be cancelled or suspended);
• the supplier is filing returns and paying the tax they collect from you.

Someone who knows the checksum formula can create a number that passes this test. That is why, for any supplier you deal with regularly or pay a large amount, the portal search is essential.

How to check status on the GST portal

1. Go to the GST portal and open Search Taxpayer, then Search by GSTIN/UIN.
2. Enter the GSTIN and the captcha.
3. Check the legal name and trade name against the invoice, the status (Active, Cancelled or Suspended), the date of registration, the constitution of business, and the taxpayer type (regular or composition).
4. Where shown, look at the return filing record to see whether the supplier files GSTR-1 and GSTR-3B regularly.

A composition taxpayer cannot charge GST on its bills. If the portal shows the supplier is under composition but the invoice charges GST, you should not claim that tax as credit.

Why checking a supplier's GSTIN protects your input tax credit

For a registered business, input tax credit (ITC) is real money. It is the GST you paid on purchases, which you use to reduce the GST you pay on sales. That credit depends heavily on your supplier.

• Your credit is generally available only if the invoice appears in your GSTR-2B, which happens only when the supplier reports it in their GSTR-1 against your GSTIN.
• If the supplier's GSTIN is fake, cancelled, or not theirs, the invoice will not appear, and credit you have already taken may need to be reversed with interest.
• If the supplier collects GST from you but does not pay it to the government, the law allows the department to deny or recover your credit.

Running a quick format check while entering a new vendor, and a portal check before the first payment, removes most of this risk.

What is at stake: a simple illustration

Say you buy goods worth ₹4,00,000 plus 18% GST from a new supplier. You pay ₹4,72,000, of which ₹72,000 is GST that you expect to set off against the GST on your own sales.

If the supplier's GSTIN on the invoice has a typing error, their GSTR-1 entry either fails or goes against the wrong number. The ₹72,000 does not appear in your GSTR-2B, and you cannot claim it until the supplier corrects it. Meanwhile, you pay that much more GST in cash on your sales. If the GSTIN was cancelled before the invoice date, the credit may not come at all, and you would have to recover the ₹72,000 from the supplier.

A ten-second check before the purchase order, and a portal check before payment, is far cheaper than chasing that money later.

Red flags on an invoice

• The GSTIN fails the check here, or its PAN type does not match the business name (for example, a "Pvt Ltd" with a P-type PAN).
• The state code does not match the supplier's address on the invoice.
• The invoice charges GST but the portal shows the supplier is under composition.
• The portal shows the registration as cancelled or suspended, or the legal name is entirely different.
• The return filing record on the portal shows long gaps in GSTR-1 or GSTR-3B.
• The supplier insists on cash payment for the GST part, or offers a lower price "without bill".

None of these alone proves fraud, but each is a reason to pause and verify before you pay or claim credit.

Practical uses: when to run a GSTIN check

Onboarding a new supplier

Ask for the GSTIN on the vendor form, check it here for typing mistakes, then verify the name and status on the portal. Save a screenshot of the portal result with the vendor file. If the supplier says it is a micro or small enterprise, also collect its Udyam registration certificate, because payments to such suppliers have to be made within set time limits. Our MSME category checker explains the categories.

Before raising a sales invoice

Your customer's GSTIN goes on your invoice and into your GSTR-1. If you type it wrong, your customer will not see the invoice in their GSTR-2B and cannot claim credit. A check here before you save the invoice avoids that.

Before paying a large bill

For one-time or high-value purchases, recheck the supplier's status on the day of payment. A registration can be cancelled or suspended between orders.

Cleaning up your vendor master

Once or twice a year, run through your supplier list. Remove or flag any GSTIN that fails the check, and verify status for active suppliers on the portal.

When a B2C customer asks for a GST bill

Sometimes a walk-in customer asks you to put their business GSTIN on the bill so they can claim credit. Check the number here before you print the invoice. Once a B2B invoice goes into your GSTR-1 with a wrong GSTIN, fixing it needs an amendment, and the customer's credit is delayed until then.

Before filing GSTR-1

Your GSTR-1 lists every B2B invoice against the buyer's GSTIN. The portal rejects numbers that are badly formed, but a valid-looking number that belongs to someone else will go through and send your customer's credit to the wrong business. A final check of new customer GSTINs before you file each month keeps your returns clean and saves your customers from chasing you for corrections.

Keeping GSTINs right in spreadsheets

If you keep vendor or customer lists in a spreadsheet, store the GSTIN column as text, avoid extra spaces, and use capital letters. When importing data into billing or accounting software, spot-check a few numbers here, especially ones starting with 0, which spreadsheets often damage.

Worked examples: reading the checker's result

Example 1: A valid company GSTIN

You enter 27AAACR5678M1ZQ. The checker shows: valid format, state Maharashtra (27), PAN AAACR5678M, taxpayer type Company (fourth PAN letter C), registration number 1, check digit Q. If the invoice is from a private limited company in Pune, this is consistent. Now confirm the legal name on the portal.

Example 2: Same PAN, different state

You enter 29AAACR5678M1ZM. It is the same PAN as Example 1, but with state code 29 (Karnataka) and a different check digit, M. A business needs a separate GSTIN in each state where it has a place of business, so the same company can hold both numbers. Make sure the invoice shows the GSTIN of the branch that actually supplied you.

Example 3: A typing mistake

You enter 09AAFFG4312H2ZK. The checker says the check digit does not match and the last character should be L. Compare it with the original document: the correct number is 09AAFFG4321H2ZK, a firm (F) with its second registration in Uttar Pradesh.

Example 4: Wrong length

You enter a number with 14 characters. The checker says a GSTIN has exactly 15 characters. Usually a character was missed while copying, often the leading zero of the state code.

Common mistakes and what they mean

• Letter O typed instead of zero, or I instead of 1. The pattern positions are fixed — digits in positions 1–2 and 8–11, letters in 3–7 and 12 — so a letter in a digit position fails the pattern test.
• Dropping the leading zero. Codes like 07 and 09 become 7 and 9 in spreadsheets that treat the column as a number. Format GSTIN columns as text.
• Using the PAN instead of the GSTIN. A 10-character PAN fails the length test. The GSTIN is longer and starts with the state code.
• Using the head office GSTIN for a branch supply. Each state registration is separate. The GSTIN on the invoice should be the one from which the goods or services were supplied.
• Trusting a valid format alone. A correct check digit is not proof of an active registration.

GSTIN, PAN, ARN and UIN: how they differ

People often mix up the different numbers that appear around GST registration. Each one has a separate job, and only the GSTIN belongs on a tax invoice.

From application to GSTIN

A business applies for registration on the GST portal with its PAN, Aadhaar authentication of the proprietor, partners or directors, address proof for the place of business and bank details. On submission, the portal gives an ARN. After the officer approves the application, the GSTIN is allotted and the registration certificate can be downloaded from the portal. Until then, the business should not charge GST.

Showing your own GSTIN correctly

Once you have a GSTIN, it must be printed on every tax invoice, credit note, debit note and bill of supply you issue. You are also required to display the registration certificate at your principal place of business and the GSTIN on the name board at the entry. Run your own number through this checker once and save it in your billing software exactly as shown, so it never goes out with a typo.

One PAN, many GSTINs

A business that operates in several states needs a separate GSTIN in each state where it has a place of business. All of them share the same PAN in characters 3–12, which makes it easy to see that they belong to the same legal entity. Each GSTIN files its own returns, and credit in one state cannot be used directly in another.

Special registrations the checker may not recognise

This tool is built for regular GSTINs, which cover almost all businesses. Some special registrations use a different structure. Examples include government departments registered as tax deductors under GST, Unique Identification Numbers (UIN) issued to bodies such as embassies and UN organisations, and non-resident providers of online services.

Some of these may show as "not valid" here even though they are genuine. If you deal with such a registration, verify it directly on the GST portal search, which covers both GSTINs and UINs.

What to do if a GSTIN fails or looks wrong

1. Recheck the number against the original document character by character.
2. Ask the supplier or customer to send their GST registration certificate or a portal screenshot.
3. Verify the name and status on the portal.
4. If you already reported a wrong GSTIN in your GSTR-1, correct it through an amendment in a later return, within the time allowed, so that your customer gets the credit.
5. If a supplier's registration turns out to be cancelled or not theirs, hold payment of the GST part until it is sorted out, and take advice on any credit already claimed.

If you do not have a GSTIN of your own yet and your customers are asking for one, our GST registration service can handle the application end to end.

Get it checked by an expert

A wrong or inactive GSTIN can quietly block your input tax credit for months before anyone notices. TaxCaller's GST expert can review your vendor list, verify supplier registrations on the portal, match your purchase records with GSTR-2B and fix GSTIN errors in your returns. The fee is told upfront before any work begins, and your first call is free.