Look up almost any PIN code and you will see post office names ending in "H.O", "S.O" or "B.O". These are not decorations. They tell you where the office sits in India Post’s hierarchy, and that in turn explains why some PIN codes cover one office while others cover seventy.
The figures below come from India Post’s All India Pincode Directory (data.gov.in, 2021 snapshot), the same data used across this site.
General Post Office (GPO)
A GPO is the main post office of a large city, usually a state capital. It is a head office with a bigger role: it handles very large volumes, often runs late-night counters, and anchors the city’s mail. The directory lists 26 offices with GPO in their name, including New Delhi GPO and Mumbai GPO. A GPO’s PIN code is the code for its own delivery area, not for the whole city.
Head Post Office (HO or H.O)
A head office administers a group of sub offices and keeps their accounts. There are 784 head offices in the directory besides the GPOs. Most district headquarters towns have at least one. A head office is still a post office in its own right — you can buy stamps, book Speed Post or open a savings account there — and many head offices also deliver mail to the streets around them.
Sub Post Office (SO or S.O)
Sub offices are the everyday post offices of towns and city neighbourhoods. The directory lists 24,615 of them. Each reports to a head office. In cities, the sub office is normally the office that gives an area its PIN code: Connaught Place, Koramangala or Andheri East each have their own sub office and their own code.
Branch Post Office (BO or B.O)
Branch offices are the small offices that serve villages. They are run by Gramin Dak Sevaks — rural postal staff, often working from a room in the village — and they handle basic counter work and local delivery. Branch offices are by far the largest group: 131,631 of the 157,056 offices in the directory, or about five in every six.
A branch office does not get its own PIN code. It reports to a sub office and shares that office’s code. That is why a rural code such as 515631 lists Tadimarri S.O and fourteen branch offices, and why one code in Chhattisgarh’s Bastar district covers 72 offices.
How they fit together
- Branch offices report to a sub office and use its PIN code.
- Sub offices report to a head office, but usually have their own PIN code.
- Head offices report to a postal division, which sits under a region and a circle (roughly a state).
- A GPO is a head office for a big city.
Which PIN code should you use?
Always the code of the office that delivers to the address. For a city flat that is normally the local sub office. For a village it is the code shared by the branch office and its parent sub office. Do not use a head office or GPO code just because it is the "main" office; mail will still get there, but it can take an extra sorting step.
Every post office page on this site shows the type, the delivery status and the other offices that share the same code. Browse by state and district, or detect the PIN code for your current location.
Is an "extension counter" a post office?
Extension counters are small counters set up inside places such as courts, ministries or hospitals so staff and visitors can use postal services on site. They appear in the directory under the PIN code of the area, but they are not delivery offices, so never address mail "to" a counter.
FAQ
Can a branch office have its own PIN code?
In the directory, branch offices use the code of the sub office they report to. If a branch office is upgraded to a sub office, it can be given a code of its own, which is one of the ways new PIN codes appear.
Why do some office names end in "S.O" and others in "SO"?
It is only a spelling difference between postal circles. India Post’s data writes the suffix in several ways — "S.O", "SO", "H.O", "HO", "B.O" — and this site keeps the names exactly as published.