Current posting profile is defined on the ledger & Sales Tax fasttab on AP parameter page where the posting profile will assign automatically when the user create a line in AP vendor journal.

The gaps are:

when there is multiple posting profiles are setup for different vendor, the default could only select one and it could be incorrectly posted when the user forget to update the posting profile.

There is a setup under AP- Setup - Vendor posting profile to assign account/vendor code for each posting profile, but it doesn't default when entering AP invoice journal.

Improvement:

Require to leave the AP parameter to be blank, so the system will use the posting profile setup under Vendor posting profile in AP invoice journal creation.