Go to Manage → Settings → VAT rates. Add a rate per country:
- NL: 21% standard, 9% low
- BE: 21% / 12% / 6%
- DE: 19% / 7%
- Etc.
For each client you choose in the client settings which rate applies by default. At invoice level you can choose a different rate per invoice line.
VAT exempt (e.g. coaching hours, intra-community services): rate 0% with a fixed reason text that appears on the invoice (e.g. "VAT reverse-charged under art. 12bis VAT Act").