Here in Europe the process to make all transactions digital has started with Italy which was appointed, sadly because of a large amount of VAT frauds, as the first nation to adopt digital invoices.
Basically they are an XML file. You can find the format here: https://www.fatturapa.gov.it/export/fatturazione/en/normativa/f-2.htm?l=en
I know that it is almost impossible for you to adopt all legal fantasies of nations around the word, but maybe you can create an instrument to save, or better export, data of an invoice based on an XML tamplate that each one can create/import and compile with Manager’s variables… something very similar to an invoice theme.
Done that, adding a button on each invoice, “save as XML” would solve this problem that every European guy will have in the near future (and Italians already have!).
PS: Perfection would be to have also an import function for XML file into suppliers invoices…