Duplicate payment

Finance teams expect a second payment to announce itself as a break in the numbers, and it almost never does. The extra cash genuinely leaves the bank, so the counterparty balance genuinely moves; what is missing is anything left visibly outstanding. Turkish ledgers are kept as a running current account per counterparty, the cari hesap, and local systems tend to apply an outgoing payment to the oldest open item on that account with little intervention. The second outflow therefore lands on the next invoice in the queue, that invoice looks part-settled, no item is stranded, and the account simply carries a balance that is quietly lower than the underlying invoices support. Repeat that a few times and a payables account drifts into a credit balance, which is the first symptom that is hard to explain away.

The cause is structural rather than careless: there is more than one way to start a payment. An invoice arrives by e-mail and again on paper and two people book it. An urgent item is paid by hand in the bank portal on Friday and then rides along in Monday's payment file. A transfer bounces for a technical reason and is repeated before the return has been booked. The same supplier exists twice in the master data, once per delivery site. An advance is paid and never offset against the invoice that follows it. Group companies that trade with each other add a layer, because one liability is carried in two ledgers under two different item numbers. The traces worth flagging all sit at line level: two outflows of the same amount to the same counterparty within a short window, two descriptions pointing at a single invoice number, a manual payment reappearing in the next batch file, and a payable account that has turned into a credit balance. The counterparty's own statement is the strongest second check, because an overpayment usually sits on their side as a credit they have not applied. A flag is a candidate for review rather than a verdict, and the correction is an accounting decision.

Three assumptions keep the problem alive. The first is that it is rare and small. APQC benchmarks put duplicate and erroneous payments at roughly 0.8 percent of annual disbursements for top-quartile organisations and 2 percent for the bottom quartile, which is a material number once volume is large. The second is that the money comes back by itself: an overpayment sits with the supplier as an unclaimed credit, is netted against later invoices without anyone deciding to, and can stay inside the relationship for years. The third is that it is merely a bookkeeping correction, when it also overstates cash actually used, distorts the forecast, and leaves a difference that has to be explained at period end. Recovering an overpayment months later is a negotiation; catching it in the same month is a reconciliation task.