RSM, the fifth largest accounting firm in the United States, is expanding its transatlantic alliance to include Mexico alongside existing members the UK, Ireland and Canada, as mid-tier accounting firms face growing pressure from private equity-backed rivals pursuing aggressive international consolidation, as reported by the Financial Times. The development directly involves RSM Ireland, which joined the original transatlantic partnership last year, and has broad implications for how accounting firms structure cross-border service delivery and partner remuneration.

The Financial Times reported that the addition of Mexico was announced to partners at a gathering in Las Vegas on Monday. The move is one of a series of reforms designed to integrate firms within RSM's global network more tightly, as competitors including Grant Thornton pursue their own international expansion plans backed by outside capital.

Brian Becker, chief executive of RSM US, said the partnership was designed to help clients receive borderless service and told the Financial Times: "Geopolitically, we're drifting further apart in our countries, but our clients want borderless service. Our mission is making sure we don't let the geopolitical noise get in the way of helping our clients be successful."

Mexico's 1,200 employees bring the total staff across the transatlantic partnership to more than 25,000, accounting for more than 40 per cent of RSM's global network. Becker confirmed the partnership is actively seeking additional member firms to join.

Under the transatlantic structure, firms jointly pitch for work, share revenue and pool profits for the purposes of calculating partner retirement payments. RSM US acquired its Canadian sister firm in 2017, and last year formalised the arrangement with RSM UK and RSM Ireland. Rob Donaldson, chief executive of RSM UK, described the structure at the time as an alternative to outside investment.

Becker will also join the governing board of the global network, which spans accounting firms in 120 countries, from 1 July. The restructured oversight model is designed to give greater influence to the largest member firms, direct more investment across the network and ensure consistent service standards for cross-border clients.

Access the full report on RSM's transatlantic alliance expansion.