Isle of Man based International Financial Group Limited has completed the deal to buy Sovereign Pension Services Limited.
Work will now be done to rebrand SPS as IFGL Pensions by the middle of the year.
The company will continue to be based in the Wirral, where it employs 45 staff, while IFGL has 450 employees across its Douglas and Castletown offices.
Chief Executive David Kneeshaw says they have ambitious plans for their future, and this will provide a wider range of services and value to customers and advisers.