A normal PAN-based GSTIN has 15 characters: positions 1–2 are the state/UT code; 3–12 reproduce the PAN; position 13 is the entity number for registrations under that PAN in the state; position 14 is normally the default letter Z; and position 15 is an alphanumeric checksum. Format validity does not prove that registration is active.
How this 2026 guide was prepared
The supplied draft was treated as a topic brief, not as legal authority. Outdated portal dates, overbroad thresholds, invented procedures and incorrect rate or format claims were corrected against official GST, CBIC, GST Council and India Code materials available on 2026-07-28.
Effective-date warning: GST rates, exemptions, portal screens and due dates can change. Confirm the live notification and return period before acting.
The exact structure
Example: 29ABCDE1234F1Z7. Here 29 is Karnataka; ABCDE1234F is the PAN; 1 is the entity code; Z is the default 14th character; and 7 is the checksum. The supplied draft reverses the last two fields and labels PAN’s own final character inaccurately as a check digit.
State code
The first two numeric characters use the GST state and union-territory code. State code validates location syntax but does not reveal ward, jurisdictional officer or the taxpayer’s branch address.
PAN segment
Positions 3–12 exactly reproduce the taxpayer PAN for ordinary PAN-based GSTINs. PAN has its own structural conventions; a GSTIN validator should compare this segment with the known PAN rather than inventing meaning for each PAN character.
Entity code, Z and checksum
Position 13 distinguishes registrations under the same PAN in the same state using the permitted alphanumeric sequence. Position 14 is normally Z by design. Position 15 is the checksum computed from the preceding characters and can be a letter or number.
Verification versus syntax validation
A regex and checksum only show that a string is structurally plausible. Use the official Search Taxpayer service to confirm legal name, trade name, status, registration date, taxpayer type, principal place state and return-filing details exposed by the portal.
Dummy GSTINs and privacy
Do not publish a guessed ‘dummy’ number that might pass validation or belong to a real taxpayer. In tests, use clearly synthetic fixtures in non-production environments, mock the verification service, and label examples as illustrations—not transaction identifiers.
Need a transaction-specific GST review?
Check registration, classification, value, place of supply, input credit, documents and return treatment before filing.
Request GST supportFrequently asked questions
What is the 14th GSTIN character?
It is normally the default letter Z.
What is the 15th character?
It is an alphanumeric checksum.
Can the entity code exceed 9?
The 13th position is alphanumeric so additional registrations can use the prescribed sequence.
Does a valid checksum prove registration is active?
No. Check the official GST Portal.
Is the GSTIN the same as PAN?
No. It embeds the PAN within a state-specific 15-character identifier.
Can I identify the officer from GSTIN?
No. The state code is not a ward or officer code.
Is 27AAAAA0000A1Z5 safe test data?
Do not assume any plausible GSTIN is harmless; use controlled synthetic fixtures and mocks.
