I have concluded that the "final posting date" in the invoice details are not correct.
I now understand that this information is not synced between the finance system and Medius.
I hope you will consider creating a sync between the finance system and medius, so this information becomes reliable.

This is an issue in at least two areas.
First, when you see the date in Medius it should be reliable.
Second, when i want to print invoice documentation from medius i don't get the "correct" invoices for a accounting period. An example is that i seek out invoices via the invoice dashboard with final posting date in marts (1/3-31/3). But since this data is not correct in Medius, then i will not get the invoices that match the vouchers in the finance system.

So, please consider syncing this datafield.
to me it is very important.