Why does the IRS have its own zip codes in the United States?

Question

Why does the IRS have its own zip codes in the United States?

In: 76

Answer 1

There are such things in the UK as “Large User Postcodes”, where organisations that get very large amounts of mail can apply for their own postal code. This improves efficiency of the postal system as they can have their mail prioritised and seperated out from the mail in the rest of the geograpical region, also lessening the impact on other customers.

I imagine it’s the same situation in the US.