Learn what a GST Number ( GSTIN ) is, its 15-digit format, benefits, required documents & easy online registration process. GSTIN is a unique 15-digit identifier for businesses registered under GST in India. Essential for tax compliance, it helps in GST filings, invoicing, and verification. GSTIN (Goods & Services Tax Identification Number) is a 15-digit unique identifier assigned to every GST-registered taxpayer in India. Learn how to apply for GSTIN , its format, benefits, and how to verify GSTIN online or offline. Within the framework of the GST Act, both businesses and individuals are mandated to register their entities with state authorities, procuring a distinctive 15-digit identifier known as the Goods & Services Tax Identification Number (GSTIN). GSTIN, or Goods and Services Tax Identification Number, is a 15-digit unique number assigned to every taxpayer registered under GST. The PAN and state of a business are represented by GSTIN. The breakdown of GSTIN is as follows: The first two digits of GSTIN indicate the C ode of a State.