The production office is, you guessed it, the office where the production is based. All paperwork goes through here at some point or another. Also, every single phone call.
We’re the home base, the steady rock on which the ever-mobile shooting crew rests.
People often found in the production office are the (line) producer, the producer’s assistant, the UPM, the production coordinator, the assistant production coordinator, and the office PAs. Usually, accounting and the writing offices are nearby. Less often, but still fairly common, the art department, props, locations, set dec are in the same building, as well.
Some in the crew crew refer to it as “the PO,” but since that can be confused with a purchase order, don’t do that. We just call it “the office.”