German to English Bus/Financial Law: Taxation & Customs

A document that is part of a lawsuit involving import duty repayments includes a memo explaining the term "fiscal representation". This refers to reporting/declaration obligations (towards Germany) of Swiss traders who import EU goods via Germany and resell them to end-users/ "Abkäufer" in other EU states.

I know that abkaufen means 'to buy from', but can't think of an appropriate noun. Or perhaps the 'ab' prefix is irrelevant and one should just say "buyers."?