Derive the correct VAT number (HQ Registration number) in AR

Cst has one Legal Entity with 10 Operaring Units. Each OU has its own establishment with its own VAT Registration Number.

When non-inventory items are used or memo lines the system uses the HQ Registration number from the main Establishment instead of the VAT number that is defined in the establishment for that OU.

So in the tax details in the AR Transactions are displaying the wrong VAT-number.

The same issue is also happening for transactions that are imported from a lagacy system. The lines have no items that are defined as an item in a inventory organization.

Thanks in advance for your reaction