What Do the 15 Characters of a GST Registration Number Mean?

A GSTIN is always 15 characters long and every character is assigned, not random. Rule 10(1) of the CGST Rules, 2017 fixes the format in four parts, which the number reads out across five positions:

• First 2 digits: the State or Union territory code of the registration, on the Census of India series. 09 is Uttar Pradesh.
• Next 10 characters (3rd to 12th): the holder's Permanent Account Number, or, on a tax deductor's or tax collector's registration, the Tax Deduction and Collection Account Number.
• 13th character: how many registrations that PAN already holds in that State. 1 for the first, then 2 to 9, then A to Z.
• 14th character: the second half of the entity code, filled with Z on an ordinary registration and with another letter where the registration is not an ordinary one.
• 15th character: a checksum computed from the first fourteen characters, which catches a typing error but never a lie.

Rule 10(1) of the CGST Rules, 2017 is the provision that fixes this format, and it allots the fifteen characters in four parts: two characters for the State code; ten characters for the Permanent Account Number or the Tax Deduction and Collection Account Number; two characters for the entity code; and one checksum character. A registration taken as a tax deductor under section 51 or as a tax collector under section 52 is the case in which characters 3 to 12 carry a TAN rather than a PAN. The GST registration certificate in Form GST REG-06 prints [See Rule 10(1)] on its own face, directly beneath the form number, so the citation is checkable on a document the registered person already holds.

Compare characters 3 to 12 of the number against the PAN you already hold for that supplier. That check proves the format only: it does not tell you the registration exists, and it does not tell you the registration is live.

Rule 10(1), Central Goods and Services Tax Rules, 2017 assigns the Goods and Services Tax Identification Number in 15 characters, subject to the following characters, namely: "(a) two characters for the State code; (b) ten characters for the Permanent Account Number or the Tax Deduction and Collection Account Number; (c) two characters for the entity code; and (d) one checksum character." 27ABCDE1234F1Z5 is an illustrative format example. It is not a real GSTIN, ABCDE1234F is not a real PAN, and the final character is not a computed checksum.

Read the number in front of you from the left, two characters at a time. Using 27ABCDE1234F1Z5 as the demonstration:

27 is Maharashtra. The registration was granted by Maharashtra, so the supplier's principal place of business for this GSTIN is in Maharashtra, whatever address is printed on the letterhead.

ABCDE1234F is the holder's PAN. If the supplier's PAN on your vendor master is not ABCDE1234F, this GSTIN does not belong to that supplier.

1 is the thirteenth character. This is the first registration this PAN holds in Maharashtra. A second Maharashtra registration against the same PAN would read 2 in the same position.

Z is the fourteenth character, and it marks an ordinary registration.

5 is the fifteenth character, the checksum. It closes the number and tells you nothing about who holds it.

Rule 10(1) allots two characters to the entity code, not one. Characters 13 and 14 are that entity code. Splitting them into "registration serial" and "default Z" is how the portal fills them, not what the rule requires.

A GSTIN does not always carry a PAN. Rule 10(1)(b) allows the Tax Deduction and Collection Account Number in characters 3 to 12. A registration taken as a tax deductor under section 51 or a tax collector under section 52 carries a TAN there.

A 14th character that is not Z is a reason to search the number, not proof that it is fake. Rule 10(1) does not prescribe Z. GSTN's own Search Taxpayer manual illustrates an SEZ Unit registration whose 14th character is not Z. Run the number through Search Taxpayer and read the answer off the portal.

Yes. "GST registration number", "GST number" and "GSTIN" all name the same thing: the Goods and Services Tax Identification Number. Rule 10(1) of the CGST Rules, 2017 is what creates it, and the rule assigns it the moment a registration application is approved. The number is printed on the registration certificate in Form GST REG-06 and must appear on every tax invoice you issue. It is granted State by State, so a business operating in three States holds three different GSTINs against one PAN. A GSTIN is not an ARN: an ARN tracks a pending application, and a GSTIN is issued only after approval.

Rule 10(1) was amended by Notification No. 18/2025-Central Tax dated 31 October 2025, with effect from 1 November 2025, to cover registrations granted under rule 9A and rule 14A as well as rule 9, and the 15-character format is identical on all three routes. A reader whose application has not yet been approved has an ARN and no GSTIN, and can track it by ARN instead. Your own number is printed on the certificate in Form GST REG-06, made available on the common portal once the application is granted, which is how GST registration works from application to certificate.

Verify a GSTIN on the GST portal at gst.gov.in, using Search Taxpayer. No login, no password and no fee are needed. The portal answers with a block headed Search Result based on GSTIN/UIN, carrying the taxpayer's profile. GSTN's own manual states the scope plainly: the Search Taxpayer functionality lets you view the profile of any other registered taxpayer on entering the GSTIN/UIN. Logging in adds fields; it does not change the answer to "is this number real". The government portal is the authoritative source, and every third-party lookup tool is reading the same GST system behind the scenes.

• Open gst.gov.in and click Search Taxpayer.
• Select Search by GSTIN/UIN and enter the 15-character number.
• Type the captcha, click SEARCH, and read the profile the portal returns.

The captcha field is labelled Type the characters you see in the image below. Those three steps are the whole verification process, and it runs online, without an account and without a fee. After logging in, the captcha step disappears and the result adds a Profile tab and a Place of Business tab. Neither changes the answer to whether the number exists.

A number that has never been issued returns no Search Result based on GSTIN/UIN block at all. Nothing is displayed to decode, and that absence is the answer.

The result also carries Administrative Office and Other Office, which is where the assigned State and Centre jurisdictions appear. Administrative Office is the office holding the file, and the tag beside it, (JURISDICTION - CENTER) or (JURISDICTION - STATE), says which administration that is. What that means for your registration is a different question, answered under what the jurisdiction tag means.

The pre-login result returns thirteen things about the taxpayer, and six of them decide whether you should transact. Legal Name of Business is the name in the PAN database. Trade Name is the name the business trades under, and GSTN states that the trade name of the business is different from the legal name of the business. Effective Date of registration is the date from which the registration runs. Constitution of Business names the entity type. GSTIN / UIN Status is the live status. Taxpayer Type names the registration category: Regular, SEZ Unit, Composition and others.

The portal's own labels are inconsistently cased, so reproduce them exactly rather than tidying them. Effective Date of registration carries a lower-case r beside title-cased neighbours, GSTIN / UIN Status puts spaces around the slash where GSTIN/UIN of the Taxpayer does not, and the two adjacent collapsibles differ by one letter's case.

Logging in adds Date of Registration, Annual Aggregate Turnover, Gross Total Income, % of Tax Payment in Cash, Name of the Proprietor / Director(s) / Promoter(s), an E-WAY BILL HISTORY button and a LIABILITY PAID PERCENTAGE button. The GSTIN's existence is established independently of these additional post-login fields. Two labels also change with the login state: post-login the status field is GSTIN/UIN/Temporary ID Status and the date field is Date of Registration.

A GSTIN is fake or dead in one of four ways, and the portal exposes all four. The number may not be 15 characters, in which case it is not a GSTIN at all. Characters 3 to 12 may not match the supplier's PAN, in which case the number belongs to somebody else. The number may return no result, in which case it was never issued. Or GSTIN / UIN Status may read Cancelled, Cancelled suo-moto or Suspended, each carrying an (Effective from …) date. Checksum arithmetic catches none of this, because a fabricated number can be built to satisfy any published checksum.

• Count the characters first. A GSTIN has exactly 15 characters. Anything shorter or longer is not a GSTIN, whatever it is labelled on the invoice.
• Match characters 3 to 12 to the supplier's PAN. Characters 3 to 12 are the holder's PAN under Rule 10(1)(b). If they do not match the PAN you hold for that supplier, the number is not that supplier's.
• Match the first 2 digits to the State. The first 2 digits are the State code of the registration. A Maharashtra address on an invoice quoting a GSTIN beginning 07 needs an explanation.
• Search the number at Search Taxpayer > Search by GSTIN/UIN. A number that was never issued returns no Search Result based on GSTIN/UIN block at all.
• Read GSTIN / UIN Status and the (Effective from …) date together. Cancelled suo-moto (Effective from 01/06/2021) means the registration died on that date, not on the date you searched.
• Check Legal Name of Business before Trade Name. GSTN states that the trade name of the business is different from the legal name of the business, and Additional Trade Name may hold a third name. Open all three before calling a mismatch.
• Read Taxpayer Type. Unregistered Applicant means the number is a Temporary ID, not a GSTIN. A Temporary ID is also 15 characters long, and its characters 3 to 12 are digits rather than a PAN.
• Open SHOW FILING TABLE for the invoice period. A supplier who filed no outward-supplies return for that period will not appear in your GSTR-2B, whatever the invoice says.

Character 15 is a checksum, and it is the least useful character on the number. A checksum catches a typing error; it does not catch a lie. Anyone fabricating a GSTIN builds it to satisfy the same arithmetic, so an "internally valid" number proves only that whoever typed it could count. This page therefore publishes no checksum formula. The validity of a registration is a fact held on the portal, and Search Taxpayer on gst.gov.in is the only test that answers the question you are actually asking.

Section 16(2) of the CGST Act, 2017 makes your credit depend on the supplier, not on the paper you hold. Section 16(2)(a) requires a tax invoice issued by a supplier registered under this Act, so an invoice from a cancelled or non-existent GSTIN fails at the first condition. Section 16(2)(aa) requires the supplier to have furnished the invoice in the statement of outward supplies and the details to have reached you, which is your GSTR-2B. Section 16(2)(c) requires the tax charged to have been actually paid to the Government. The invoice, GSTR-2B and tax-payment conditions must each be satisfied independently of payment to the supplier.

The credit is denied to the recipient, and recovering the loss from the supplier is a contractual matter rather than a GST remedy. A registration cancelled with retrospective effect is the sharpest version of the problem, because the (Effective from …) date can precede invoices you have already paid and already claimed. The cheapest control is to verify the GSTIN once at onboarding and re-check GSTIN / UIN Status before the first payment of each quarter, since the status changes and the invoice does not.

Stop before you claim the credit, and work from the (Effective from …) date. Save or print the Search Result based on GSTIN/UIN page with the date of your search; that screen is your evidence and it is not archived anywhere for you. Reconcile the invoice against your GSTR-2B for that period, because an invoice from a cancelled registration will not be there. Write to the supplier asking for the correct GSTIN and a fresh tax invoice, or a credit note against the one you hold. Do not net the GST off the payment without an agreement that says you may.

Where the cancellation is retrospective, list every invoice from that supplier dated on or after the (Effective from …) date, not only the one in front of you. Where the number returns nothing at all, treat the supplier as unregistered from the start and check whether the invoice charged GST it was never entitled to charge. Where the status reads Suspended, the registration may be restored, so hold the credit rather than writing it off, and re-search before the return due date. This practice handles that reconciliation and the correspondence with the supplier where a client asks.

There is no dedicated channel for reporting somebody else's fake GSTIN. The nearest route is the Grievance Redressal Portal for GST, linked from the gst.gov.in footer, which is a general GST grievance channel and not a fake-GSTIN reporting facility.

Search by PAN at Search Taxpayer > Search by PAN on gst.gov.in, which is the sibling of Search by GSTIN/UIN in the same menu. The PAN search returns every GSTIN registered against that PAN across India, with the State and the status of each. GSTN's registration manual describes the same behaviour inside the application flow: the GST Portal displays all the GSTINs, Provisional IDs, UINs and GSTP IDs mapped to the same PAN across India. There is no search by business name on the GST portal. The third item in that menu is Search Composition Taxpayer, which is not a name search either.

The PAN search is the right tool when a supplier trades in several States and you have one of their numbers but not the one on this invoice. A name-based lookup is offered only by third-party tools built on GSTN's data, and their coverage and freshness are their own rather than the portal's.

Run your own PAN through Search Taxpayer > Search by PAN at least once, because the result lists every registration anyone has taken against it, and the portal provides a means of reporting a registration you did not apply for. That route reports a registration on your own PAN, and it is not a channel for reporting a supplier's fake GSTIN.

A PAN search cannot find an application that has not been granted, because no GSTIN exists yet: until the application is granted there is no GST registration number to find, and the application is tracked by its ARN instead.