Also called GST number, GST identification number, GST registration number
A GSTIN is the 15-character number a business gets when it registers under GST. The first two digits are the state code, the next ten are the business's PAN, then comes an entity number, the letter Z by default, and a final check character.
A business needs a separate GSTIN in every state it supplies from. You need one once your turnover crosses the registration limit, which for most sellers of goods is ₹40 lakh a year and lower in some states. Some businesses must register whatever their turnover, such as those making inter-state sales or selling through e-commerce operators, with limited exceptions.
In a GSTIN such as 27ABCDE1234F1Z5, 27 is Maharashtra and ABCDE1234F is the PAN. Checking a supplier's GSTIN before you buy matters, because a wrong or cancelled one can cost you input tax credit. Kownt X's supplier directory includes GSTIN checks.