Tax on coupon code

[kratzi]

Hi,
My questions is concerning VM 3.2.4 but I guess the behaviour is the same in the newer versions of VM.

Could please anyone help me and tell where the reduced VAT is stored in the database when a purchase is done with a coupon code. I could not find this value anywhere so far.
What I mean exactly is that when a customer places a purchase and uses a coupon code the invoice is reduced with the amount of the coupon code but also the VAT is reduced based on the reduced articles.
My problem is that we want to import the orders into another ERP but can not import the reduced VAT of the coupon code. On the VM invoice however the reduced VAT is somehow calculated.

In addition I would be interested if it is actually planned to possibly add a tick box to a coupon so the system knows if a coupon code should also reduce the VAT on a invoice or not because at the moment the coupon code reduces the VAT in any case. There are different rules in different countries if a coupon reduces the tax or not so I guess it would be nice to have a solution here one day.

Regards
kratzi