Hi @Arthur Götz
It's been a while since I used QB Desktop but I seem to remember that VAT was always a problem when importing IIF files - certainly after 2007-8 or whenever the VAT Handling method was changed in the codebase.
IIF is an Intuit format so you'd be forgiven for thinking that it would work with an Intuit product!
However, it was considered to be old & creaky and the new kids didn't want to play any more.
Sorry - I digress.
Your best bet will probably be a third-party link that will update the QBD datafile directly.
Take a look at https://www.zed-systems.com/axis-import.html or https://www.transactionpro.com/importer-for-desktop/
Hope this helps.
