The IT system crisis that plagued TSB and its customers in 2018 led the bank into a £105 million loss for the financial year.
The cost of the upgrade and compensation paid out to customers, who lost access to their bank accounts for days, totalled £330.2m. Although TSB said it recovered £153m from Sabris, the provider of the IT system.
The failure saw over 80,000 customers ditch the bank in 2018, up from 30,000 in 2017. In total, £125m was paid out in compensation to around 181,000 customers. However, a further 23,000 customer complaints are yet to be resolved.
The error came when TSB attempted to upgrade its IT system following its separation from Lloyds Bank. It occurred when customer data was transferred to the new system. It resulted in 1.9 million online and mobile banking customers unable to access their bank accounts.
Following the crisis, none of the company's executives received a bonus, though it did give the rest of its staff a £1,500 bonus in December in recognition of the extra hard work required as a result.
TSB's executive chairman, Richard Meddings, said: "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 bank's chief executive, Nicky Morgan, resigned following crisis.