Capture VAT correctly when deducting return fee from refund

[Recintegration]

I have a question regarding the best and most correct way to take out a return fee on the refund using APIs and still capture correct VAT after refund. If we use Calculate and Refund API, the return fee can be set as an order_adjustment on one of the line items. However if it is dollar amount, which can perhaps cause problems since shopify personnel says "When you manually adjust the dollar amount that is refunded to the customer, the taxes charged on the order do not change; they only change when you add or remove a line item".

Is there a way to do it better? Or can one add the tax amount needed for the deduction somehow via the API:s?

Many thanks!