The UK's Faster Payments system has not been so fast for some customers this week thanks to a system failure on Sunday that has seen thousands of transactions take two days to process.
The Faster Payments Scheme, which is used by all the major UK banks, says that it experienced "intermittent issues with its central infrastructure" for four and a half hours on Sunday afternoon.
The "vast majority" of the backlog payments were processed later that day but, nearly two days later, around 8000 were still outstanding.
Some affected customers have been hit by overdraft fees as a result of the outage, although the Faster Payments Scheme insists that no one will be left out of pocket.
In the meantime, the scheme is working with Mastercard-owned Vocalink, which is behind the Faster Payments IT infrastructure, to investigate the cause of the problem.
While details are scant, the issue is related to the central infrastructure, not the bank gateways.
Nearly a decade after launching, last year the Faster Payments Scheme began seeking 'Expressions of Interest' from tech vendors for the renewal and management of its back-end infrastructure.