The cause:
When exporting expenses from Pleo to Exact Online, some customers have seen a message saying that an expiration date (due date) is necessary in order for the export to work. This comes up because the Exact integration considers all Pleo expenses to be "invoices" (even though they're just regular card payments). Our product team is currently working with Exact to try to remove this requirement from the integration. In the meantime, though, the below solution will solve the problem.
The solution:
In Exact Online, please go to Accounts > Suppliers > Overview > Search for supplier related to the affected invoice > Edit > Creditor > Payment condition.
Select a payment condition, then set the "Payment method" to "Cash" and the number of days to "365". If you are creating a payment condition from scratch, then please select the code as "00" and the description as "Cash".
Please re-try the export from Pleo. This time it should work.