Chancellor Philip Hammond has triggered the sale of £11.8 billion worth of Bradford & Bingley loans acquired during the financial crisis.
The Government said the funds would be sold to Prudential and Blackstone and delivered "value for money" for the taxpayer.
Mr Hammond said: "The sale of these Bradford & Bingley assets for £11.8 billion marks another major milestone in our plan to get taxpayers' money back following the financial crisis.
"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 Government said the price reflected the "strong credit quality" of the portfolio and was the result of a highly-competitive sale process.
It added that borrowers would not need to take action because there would be no change to the terms and conditions of the loans sold.
UK Asset Resolution (UKAR) manages Bradford & Bingley and NRAM's closed loan books on behalf of the taxpayer.
Ian Hares, UKAR chief executive, said: "This sale of assets is a significant milestone in the phased repayment of the FSCS loan extended to Bradford & Bingley and when complete will reduce UKAR's balance sheet to £22 billion from £116 billion in 2010 when it was formed.
"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 sale is expected to be completed by 2017/18, with any further sales being made subject to market conditions, the Government added.