Edinburgh-based Aegon UK said it completed the roughly £140 million purchase of Cofunds — an investment platform for financial advisers — following regulatory approval.
Cofunds had about £77 billion of assets under administration when the deal was announced in August.
Aegon UK said the acquisition supports its strategy to be an investment trading platform business set up to serve the needs of intermediaries.
Aegon UK chief executive Adrian Grace said: “The completion takes us a major step further in our transition from traditional life company to fully-fledged platform business.
“Our focus now is to help intermediaries grow their business, grow their profitability and manage their risk and costs effectively.
“What will set us apart from the competition is our commitment not to compete with advisers for distribution, and focus on our investment trading platform and providing the best service and tools.”
Cofunds will continue to be led by David Hobbs and be run from its HQ in Witham, Essex, with operational staff also located in Hove, East Sussex.
In the UK, Aegon offers retirement, workplace savings and protection products to around two million customers and employs 2,100 staff.