In everyday use, GSTIN and GST number mean the same thing: the 15-character identifier printed on a GST invoice. If someone asks for your GST number, they want your GSTIN.
The terms are not perfectly identical, though, and the difference occasionally matters.
The strict meanings
GSTIN is the formal term. It stands for Goods and Services Tax Identification Number and refers to one specific thing: the 15-character registration identifier.
GST number is informal. It is a plain-English label people reach for, and depending on who is speaking it can loosely refer to:
- the GSTIN itself, which is what it means almost every time
- an ARN (Application Reference Number) received while a registration application is being processed
- a provisional ID issued during the original migration to GST
- in very loose speech, a GST-related reference number of some other kind
Because of that looseness, forms and contracts generally say GSTIN.
How to tell what you have been given
If a colleague hands you "the GST number" and you are not sure it is a GSTIN, check the shape:
- 15 characters, starting with two digits, with a PAN in the middle — this is a GSTIN.
- Ten characters, five letters then four digits then a letter — this is a PAN, not a GSTIN.
- A longer numeric string, often 15 digits with no letters — likely an ARN from a pending application, not a live registration.
A GSTIN is the only one of these you can use to run a GST registration lookup.
Why people conflate them
GST replaced several older registrations, and each of those had its own name — TIN, service tax number, excise registration. When GST arrived, "GST number" became the natural successor phrase and stuck, while the official documentation used GSTIN. Both survived.
Search behaviour reflects this: far more people search for "GST number search" than "GSTIN search", even though they want exactly the same result.
Does it matter which you say?
In conversation, no. In a document, prefer GSTIN. Writing "GSTIN" in a purchase order, vendor form or contract removes any doubt about which number you are asking for, and makes it clear that a PAN or an application reference will not do.
What about UIN?
There is one related identifier worth knowing. A UIN (Unique Identification Number) is issued to certain bodies such as embassies and specified international organisations so they can claim refunds. It is also 15 characters, but it is not a normal taxpayer registration. If a lookup describes a record as a UIN holder, treat it as a special category rather than an ordinary supplier.
Where to go next
- Read what is a GSTIN for the full structure.
- Read the GSTIN format guide for a character-by-character breakdown.
- Read GSTIN vs PAN to see how the two identifiers relate.
- Run a lookup with GST number search.