FPM, based in Newry, has now changed its name to AAB, two years after joining the UK group.
And HR services firm Think People, acquired by the group two years ago, has also rebranded in a move introducing leadership and development services for clients.
In addition to FPM, accountancy firms Sagars and May Figures will also become AAB.
SeeHearSpeakUp is also joining Think People to make AAB People, the full-service people consultancy arm of AAB.
AAB employs around 1,000 people across 12 office locations in Scotland, England and Ireland. It delivers audit, accounting, tax, payroll, HR, consulting and advisory services globally, with annual turnover approaching £100m.
Its growth plan is receiving continued backing from August Equity.
AAB said a transition period was now taking place so that there would be no disruption to services to clients.
Emma Lancaster, chief executive at AAB, said: “By combining our diverse services under the widely recognised AAB brand, we are not only simplifying our structure, but also amplifying our ability to deliver integrated, innovative solutions to our clients.
“This alignment is crucial as we continue to pursue our ambitious growth targets and expand our footprint in the UK and beyond.
“AAB’s commitment to our clients remains steadfast, with a focus on delivering unparalleled accountancy, consultancy and advisory services that drive success.”
Feargal McCormack, founder of FPM, and Emer Hinphey, co-founder of Think People, added: “As founders of FPM and Think People, we are both immensely proud of the milestones achieved and excited for what’s to come.
“Transitioning to the AAB brand marks a deliberate step towards our future and highlights the collective strength and shared mission of delivering outstanding service and value to clients.
“Together, we look forward to navigating this exciting new chapter of growth and possibility.”