I've noticed that for some intra-EU orders that use the Mollie module the taxes are wrong in some places and correct in others.
Settings applicable to all examples that follow: I am based in Germany. I use EU Advanced Compliance module (in case relevant) with proportional taxes for shipping. Payment using the Mollie module (not all payments via Mollie are wrong, though).
Example
An order from France. The order has items with the standard and with the reduced tax rates. These should be calculated using the French rates.
Observations
id_tax in order_detail_tax shows me only one wrong tax id (Germany, reduced) with a wrong unit_amount and total_amount. Where does this get filled from?
tax_name and tax_rate under order_detail show me only wrong German taxes, not Austrian ones.
The tb generated invoice shows me the correct French tax rates.
Where else might I want to check to figure this out?
How to check yourself
The file orders-eu-tax2.php in the excellent Prestools https://www.prestools.com/Prestools_Suite.zip can help you see if there's an issue. Looking at Austria, I can see that 5 orders (column Ordercount) use a tax rate of 7% (column Tax rate), which I know is Germany's reduced tax rate. Austria's reduced tax rate is 10%. You can click on Ordercount to see which orders are affected.