The IT outage that TSB experienced last year left the bank $137.66 million (£105.4m) in the red, the bank confirmed in its FY2018 results.
Overall, costs for the outage hit $431.3 million (£330.2m), but part of that expense will be covered by computer provider Sabis ($199.8m - £153m).
The bank also faced costs of customer compensation and fraud, roughly $163m (£125m) for compensation and $64m (£49m) for fraud. It also had to pay for help and advice, and had to tackle lost income from waived fees and charges.
TSB said it had lost roughly 80,000 customers which switched to other providers as some people were left without service for weeks. A year prior, the bank had lost 50,000 customers.
Almost all (90 per cent) of customer complaints were resolved. Out of 204,000 complaints, 181,000 was resolved, leaving 23,000 yet to be handled.
The staff (execs excluded) were rewarded, financially, for the extra work they put in to sort things out. Execs will be getting no bonuses for last year.
Richard Meddings, TSB executive chairman, said in a statement: "Last year was TSB's most challenging year. But we enter 2019 with renewed ambition to re-emerge as the leading challenger bank in the UK - firmly on the side of the customer."
The IT outage happened as the bank tried to move its data to a new computer system. The attempt backfired, leaving the bank’s users without access to online banking services for a couple of weeks.
In the aftermath, the company’s CEO Paul Pester, quit.
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