RSA said it would dispose of £834m ($1bn) of UK legacy liabilities in a deal that the insurer said will strengthen its capital position and allow it to focus on existing businesses.
The group said it will sell the liabilities to Bermuda-based Enstar Group, which specialises in buying and managing closed insurance portfolios and runs them off.
RSA said the 75% of the liabilities relate to asbestos insurance, with the rest covering abuse, deafness, marine and aviation issues. RSA runs the insurance business in the UK.
RSA is run by former Royal Bank of Scotland boss Stephen Hester who has turned the group around since he took the helm in 2014, after a £200m black hole was found in its Irish business.
Chief executive Hester said: "We are pleased to have achieved this valuable risk clean-up transaction with Enstar. It allows us to focus even more on driving the outperformance of RSA's continuing businesses."
Under Hester, RSA has sold off a number of international units in Latin America and Russia, and focused on key markets in the UK, Ireland, Scandinavia and Canada.
In November, RSA said it has benefitted from the drop in the fall in the value of the pound by some 16% since the June Brexit vote, and expected a boost in operating earnings for the tax year. Over two-thirds of the company's profits are generated overseas.