Thus, this GST number , also called Goods and Services Tax Identification Number ( GSTIN ) is basically a 15-digit number that is unique to every tax payer who is registered under GST. All you need to know about GSTIN (Goods and Services Tax Identification Number ). Know what is GSTIN , Structure, Benefits, How to Apply and Verify GSTIN . Learn everything about GSTIN : its format, how to register, search, and verify your GST number . Get step-by-step guidance for seamless GST compliance. A comprehensive guide to applying for a 15-digit GSTIN online in 2025. Learn the step-by-step process, required documents (PAN, Aadhaar, address proof), zero government fees, and how to check your ARN status.