I once spent two hours in New Orleans getting this sorted. Never had that problem in Europe, but in the US they seem to get confused with these vouchers. In my case they somehow keyed in the GBP value instead of the USD value, and even when I queried why the invoice didn’t zero out they said something like “oh it’s fine” which of course it wasn’t. The rental invoices are ridiculously difficult to read especially if there’s a voucher involved. I’m extra careful now, which doesn’t mean I will be able to avoid issues, so thanks for reminding me.