I deliver to 2 different zipcodes and was told by the district "rural expert" back in April 2022 to absolutely not change to intermediate zip, to use head-out office zipcode only. I also originally was provided cards to scan to switch zips which I stopped using in 2022. I have tracked my daily package to door volumes and my scans (including load times at both offices) are being credited to the route. The two zipcodes are similar size. I perform all RECCS scans on intermediate route except clock in/out, depart/return from route and pm casing. Boxholder scans are only used at intermediate if they get one that head-out did not receive.
Talked with union about this in 2022, they couldn't give me a definite answer but I'm comfortable now with what is being credited to route. But I have to watch when delivering foreign pkgs, accountable mail (especially certs) and pkgs that clerk has printed a new scan barcode for on intermediate rt. because the scanner defaults to the head-out office's zip in those circumstances.
Since Unclewolverine and I are following different procedures but coming to same conclusion, seems to not make much difference. Check with the union, they should have an answer for this by now.