PIN Code System India: How the 6-Digit Postal Index Number Actually Works

PIN code = Postal Index Number. Introduced on 15 August 1972 by India Post to streamline mail sorting, the 6-digit code is now used for everything from e-commerce delivery to GST registration to job applications. The structure is intentional and decodable.

The 6-digit structure

Take Mumbai's Bandra (West): 400050.

• Digit 1 — Postal zone: one of 9 zones (the digits 1-8 plus 9 for army postal services).
• Digit 2 — Sub-zone: a region within the zone, mostly state-aligned.
• Digit 3 — Sorting district: a sorting hub within the sub-zone.
• Digits 4-6 — Post office: the specific delivery post office.

The 9 postal zones

City prefix examples

• 110xxx = Delhi (zone 1, sub-zone 1, sorting district 0)
• 400xxx = Mumbai (zone 4, sub-zone 0, sorting district 0)
• 560xxx = Bangalore (zone 5, sub-zone 6, sorting district 0)
• 700xxx = Kolkata (zone 7, sub-zone 0, sorting district 0)
• 600xxx = Chennai (zone 6, sub-zone 0, sorting district 0)
• 500xxx = Hyderabad (zone 5, sub-zone 0, sorting district 0)
• 411xxx = Pune (zone 4, sub-zone 1, sorting district 1)
• 800xxx = Patna (zone 8, sub-zone 0, sorting district 0)

Look up any 6-digit PIN to find its post office, district, and state via our PIN Code Lookup.

Quirks worth knowing

Mumbai 400xxx codes sometimes route through Maharashtra's neighbours.India Post's sorting hubs aren't purely state-bound. A letter to a Mumbai PIN may transit through MP's Bhopal sorting hub if that's the more efficient routing. The PIN's first 3 digits encode the destination, not the route.

9xxxxx is reserved for the Army Postal Service (APS).Soldiers' mail uses 9-prefix codes regardless of physical location. A field post office in Ladakh and a base in Kerala both use 9xxxxx codes — APS routes them via military channels.

One PIN can cover multiple post offices. Each 6-digit PIN is shared by all post offices in its sorting region. Bangalore has dozens of post offices using 560001 (city/HPO area). The PIN identifies the sorting destination, not a unique branch.

Common use cases

• E-commerce serviceability check. Marketplaces validate delivery feasibility by PIN. Some PINs (remote areas) have higher shipping fees or no service.
• GST registration. Place of business must match PIN-state combination. Lying about state via PIN triggers verification by the GST officer.
• Bank KYC. Banks cross-check declared address against PIN-state to catch identity fraud.
• Job applications. Govt forms validate PIN against their internal address database; mismatches trigger rejections.

India Post operations

India Post handles ~14 billion mail items per year through 155,000 post offices — the largest postal network in the world. The PIN code is the spine that makes that volume routable in a country with 1.4 billion people, 28 states, 8 union territories, and dozens of officially-recognised languages.

Despite digitisation reducing mail volumes, the PIN system survives as critical infrastructure for parcels, government documents, ATM cards, passport delivery, and the Speed Post network.

Frequently asked

Why does my address have a different PIN from my neighbour's? Some areas straddle PIN boundaries. Each block / housing complex / building cluster is mapped to one specific post office. India Post's database is the authority — use our PIN Code Lookup to confirm.

Can a PIN code change?Rarely. India Post sometimes splits high-volume PINs (e.g. when a new sorting hub opens). Your address's PIN can change if your post office is reassigned to a new sorting region. Check with your local post office.