Tavistock Investments PLC (AIM:TAVI) told investors it has completed the acquisition of Alpha Beta Partners, the asset-management firm based in London and Bath with close to £3 billion in assets under management.
Since the deal was agreed in November, ownership has been transferred and an initial payment of £6 million made.
This is part of a total consideration capped at £18 million, based on ABP's financial performance over five years.
Tavistock chief executive Brian Raven said: "Completion of the acquisition marks a key milestone in the company's new strategic development to provide asset management services to regulated third-party advice firms and, in due course, directly to the public."
ABP reported annualised earnings of over £500,000 and turnover exceeding £4 million for the nine months to 30 September.
Tavistock shares were up 1.5% at 4.97p on Thursday morning.