The Indian Postal Index Number (PIN) is a 6-digit code introduced on August 15, 1972, to streamline mail delivery, with over 150,000 post offices nationwide. The first digit indicates the region, the first two digits designate the postal circle, the third indicates the sorting district, and the last three identify the specific post office.

The first digit of a PIN indicates the zone, the second indicates the sub-zone, and the third, combined with the first two, indicates the sorting district within that zone. The final three digits are assigned to individual post offices within the sorting district.