ZIP code changes

[daysleeper47]

Hi Wombat, here the post office is a goverment department, and yes, I am pretty sure that they handle zip codes. Once a zip code is changed, it is universally changed and everyone adopts the new one. The post office usually has a 2-month grace period where both will be accepted, and after that, the new ones will be the only ones used, all other mail will be reutrned to sender.

[wombat]

We have a problem down under in Vic Australia. About 4 years ago the state government changed many postcode (Zip code) boundaries around Victoria. The post office still use the old codes and don't appear to be planning to adopt the new boundaries. Ie my mail address is still XXXX. The new boundaries are supposed to be used by all government departments. Mail from my local government dept always comes addressed as YYYY. Does a cirlcle from postoffice Y where they redirect it back to X not a big problem.
The main problem is that if I report a fire at my home and use my usual postoffice address XXXX they will tell me it does not exist and insist I use the new zip code. This is alright for me as I know the rules. - - Their database reflects the new boundaries - but it must be very confusing to others.

Sorry about the long winded description but who owns and administers the Zip codes in the USA? Is it the Post Office or a government department?