Angry retailers have launched a tirade against HSBC after its e-payments system fell over on Friday and stayed down for the whole weekend.
Retailers were unable to sell anything online for over 48 hours, and have started calling for compensation.
HSBC's e-payments system has proved particularly attractive for retailers because of the relative speed in which the money is transferred into their bank account.
Payments using PayPal, one of the major alternatives, can take 5-7 days to clear.
While some retailers have multiple payment systems, those who relied on HSBC found they were unable to make any sales while the system was down.
"We have lost an estimated £8k over this weekend and we know many other firms are in a similar position," said the managing director of a legal services firm in an email to The Register.
Another reader, who works for a Hampshire-based catering company, told us: "We are still fighting for £4,000 in compensation [from an outage in January] and will add £10,000 after this incident."
Retailers also complained that HSBC had not made any effort to communicate about the outage.
Approached by The Reg, HSBC would not confirm or deny the outage, would not say how it intended to stop the problem happening again and would not say if it would compensate affected customers.
HSBC's recent experiences of web technology have been poor. Only three weeks ago, the bank forgot to renew its digital certificate, causing customers to see a message saying that its site could not be verified as secure.
It's believed that HSBC's e-payments site also went down for a day in January.