The deal will be paid in cash and shares, the groups announced late last week.
Standard Life Aberdeen will offload its insurance arm to Phoenix Group in a £3.2 billion ($4.5 billion) deal as the UK’s largest listed asset manager looks to focus on its core business.
Phoenix, the £3 billion insurer, will pay £2.28 billion in cash, and Standard Life Aberdeen will take a 19.99 per cent stake in Phoenix Group.
The sale will see recently-merged Standard Life Aberdeen break from its insurance roots.
Earlier this month, the merger’s merits were tested after Standard Life Aberdeen’s shares slipped 9 per cent after Lloyds Banking Group announced it would pull £109 billion from the asset manager next year.
Still, Sir Gerry Grimstone, chairman of Standard Life Aberdeen, said the sale to Phoenix "completes our transformation to a capital light investment business".
“This transaction represents excellent value for our shareholders, including a comprehensive and mutually beneficial strategic relationship entered into with Phoenix Group, a longstanding partner of the firm,” he said.
Phoenix Group has said it will keep Standard Life Aberdeen’s insurance arm’s operational headquarters in Edinburgh.