GSTIN
The 15-character GST registration number that identifies a business in a particular state. It appears on every tax invoice you issue and receive.
A GSTIN is your GST identity. It is 15 characters long: the first two are the state code, the next ten are the PAN of the business, and the rest are a registration counter, a fixed letter and a check character.
One business can have several
Registration is state-wise. A distributor with godowns in two states holds a separate GSTIN for each, with the same PAN inside both. That is why the state code at the front matters — it tells you which registration a document belongs to.
Why the customer's GSTIN matters to them
Your customer can only claim input tax credit if the invoice carries their correct GSTIN and you report the supply properly. A wrong or missing number on a B2B invoice means they lose the credit, and you get the phone call.
Check it before you save the party
Confirm the number against the customer's GST certificate when you create the account, not on the day of the invoice. Registrations also get cancelled — if a regular buyer's status changes, your treatment of the supply may change with it.
How KillStock handles it
The GSTIN is held on the customer and supplier records and printed on the documents that need it, so the same verified number is used on every invoice instead of being typed again each time.
A common mistake
Storing the GSTIN with spaces or in lower case. Keep one clean format — the mismatch causes trouble when your data is compared against the portal.