GST glossary
GSTIN
Goods and Services Tax Identification Number
A GSTIN is the 15-character number given to every business registered under GST, one for each state in which it is registered. It is made up of the state code, the business's PAN, an entity number, the letter Z and a check character.
Why it matters to your business
Your GSTIN is on every invoice you issue and every return you file. Your customer’s GSTIN on your invoice decides whether they get input tax credit. A single wrong character sends the invoice to the wrong business in their GSTR-2B, or the IRP rejects your e-invoice. Checking GSTINs at the time you add a customer or vendor saves you from correcting invoices later.
How it is built
As of September 2026, every GSTIN has the same 15-character structure. Taking the pattern 27 ABCDE1234F 1 Z 5 as an illustration:
| Characters | Meaning | Illustration |
|---|---|---|
| 1-2 | State code | 27 (Maharashtra) |
| 3-12 | PAN of the business | ABCDE1234F |
| 13 | Entity number for that PAN in the state | 1 (first registration) |
| 14 | Default letter | Z |
| 15 | Check character, calculated from the others | 5 |
Because the PAN sits inside the GSTIN, all registrations of one business share the same ten characters in the middle.
Where it matters most
- Place of supply: the state code of your GSTIN and the customer’s location decide between IGST and CGST plus SGST.
- Branches in other states: each has its own GSTIN, its own returns and its own credit. A transfer between them is a taxable supply.
- Vendor checks: a vendor with a cancelled or suspended GSTIN cannot pass you credit.
Common mistakes
- Copying a GSTIN from an old letterhead without checking its status.
- Billing a customer’s branch in another state with the head office GSTIN.
- Using a PAN in place of a GSTIN for a registered customer.
Questions about GSTIN
How do I check whether a GSTIN is valid?
Use Search Taxpayer on the GST portal, gst.gov.in. It shows the legal name, trade name, status (active, suspended or cancelled), the date of registration and the filing record, so you can confirm a customer or vendor before you deal with them.
Do I need a separate GSTIN for each state?
Yes. You register in every state or union territory from which you make taxable supplies. You may also take more than one registration within a state, for example for separate places of business.
When must a business register for GST?
When aggregate turnover crosses ₹40 lakh for businesses supplying only goods, or ₹20 lakh for services, in most states. The limits are lower in some special category states. Some businesses must register whatever their turnover, such as those making inter-state supplies of goods or selling goods through e-commerce platforms, subject to limited exceptions.
What do the digits in a GSTIN mean?
The first two digits are the state code (27 for Maharashtra, 29 for Karnataka, 07 for Delhi), the next ten are the PAN, the 13th is the entity number for that PAN in the state, the 14th is Z by default, and the 15th is a check character.
Updated .