Does anyone know how to look up the address "master?" id of an address off of a transaction? I can get the billaddresskey and shipaddresskey. But that seems to change from transaction to transaction. I need to query up the id as it would be on the customer/vendor/location/etc records.

is your question how to find the Customers Address from a transaction? there is no real master as the customer can have many addresses associated, there is a current default shipping or default billing address? is that what you are looking for? As to your point of the transaction address changing ID's, the transaction inherits the addresses from the customer and make a copy of the address, Thus if the customer address changes the history (and taxablility) of previous orders do not change.

I'd like to match the address on the transaction to the address on the customer and get the customer address id since that is constant. I'm integrating with a TMS and sending the transaction address id is creating multiple locations in the TMS. I'm thinking the only way to do this is to store the address internal id as a custom field on the address record. This may be the only viable workaround.