Royal Bank of Scotland is likely to get £300m less than it expected for the sale of 318 branches to Santander, the FT reports.
The price cut is due to a number of targets outlined in the deal being missed.
The report said economic decline since the deal was reached in August 2010 had limited profitability of the business, which is made up of 318 branches and 2 million retail and small business clients.
It said the agree price of £1.65bn - which included a £350m premium over the value of the business - is expected to be reduced on completion.
RBS, which is 82% owned by the government, has until the end of next year to sell the branches under European Union state aid rules.
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