Upon completion of the deal, OMX Securities will rebrand and trade as TD Waterhouse Corporate Services, Europe.
The deal will see TDWH widen its outsourced settlement and administration services to corporate clients including stockbrokers, wealth managers, fund managers and institutions.
OMX Securities currently services 22 clients, managing over £4bn in assets for over 100,000 underlying client accounts.
In February, TDWH also increased its stake in offshore online bank Internaxx and acquired the online sharedealing client base of Hoodless Brennan.
TDWH CEO Angus Rigby says: “OMX Securities is a natural and perfect fit for us. We have been successfully providing white label solutions for some time and this is an area we are keen to expand.”