+
+ # 1. $invoice->open_amount is arap.amount - ararp.paid (always positive!)
+ # 2. $bank_transaction->amount is negative for outgoing transactions and positive for
+ # incoming transactions.
+ # 1. and 2. => we have to turn the sign for invoice_amount in bank_transactions
+ # for verifying expected data, check t/bank/bank_transactions.t
+ $bank_transaction->invoice_amount($invoice->open_amount * -1);
+