OPTION 4) i.e. Goods and Services Tax Identification Number.GSTIN or Goods and Services Tax Identification Number is a unique 15-digit numberIn this, the first TWO digits DENOTE the state code while the next 10 digits denote the PAN of business entity/proprietor.The 14th digit is "Z" by default while the last digit is the check code (can be a number or an ALPHABET).