The Treasury says it expects to receive £11.8bn ($14.7bn) from a sale of Bradford & Bingley loans acquired during the 2008 financial crisis.
The sale – to insurer Prudential and funds managed by Blackstone – is part of an effort to recoup taxpayer money that was spent to bailout banks in the midst of the financial crisis.
The Treasury said the transaction delivered "value for money for the taxpayer".
Buy-to-let mortgage provider Bradford & Bingley was bailed out by the government during the financial crisis and is currently managed by UK Asset Resolution (UKAR).
The overall size of UKAR's balance sheet stands at £22bn after the sale of the loans, down from £37bn in September last year and £116bn in 2010.
"The sale of these Bradford & Bingley assets for £11.8bn marks another major milestone in our plan to get taxpayers' money back following the financial crisis," Chancellor Philip Hammond said.
"We are determined to return the financial assets we own to the private sector and today's sale is further proof of the confidence investors have in the UK economy."
The sale is the first of a programme that is designed to raise proceeds for Bradford & Bingley to repay a £15.7bn debt to the Financial Services Compensation Scheme (FSCS).
There will be no changes to the terms and conditions of the loans sold for customers, with the entire programme of sales expected to conclude before the end of the 2018 financial year.
"Any further sales will be subject to market conditions and ensuring value for money," the Treasury said.
UKAR chief executive Ian Hares added: "This sale of assets is a significant milestone in the phased repayment of the FSCS loan extended to Bradford & Bingley.
"We are very pleased with the price achieved which delivers excellent value for the taxpayer.
"The transaction delivers against our overarching objective to develop and execute divestment strategies which protect and maximise value for the taxpayer whilst treating customers fairly."
The government has also been selling off stakes it acquired in banks such as Lloyds and Royal Bank of Scotland during the financial crisis, with the proceeds being used to reduce the national debt.