Managing Partner, Tom O'Brien: Irish Times Profile

This article was published in the Irish Times on Friday, 30 January 2026.

Tom O’Brien, managing partner of Forvis Mazars, is sitting out the accountancy firm’s sponsored annual steps team challenge – a four-week slog where teams of four across the country battle the elements to clock 10,000 steps a day to start the year.

The former top GAA club footballer – whose battles on the pitch led to four nose operations and dislocated shoulders – took part in the past but says he needs a hip replacement before he can do so again.

However, O’Brien has been making strides elsewhere of late, having last year led Forvis Mazars’ Irish practice to become the sixth-largest accountancy firm in the State by revenues and seeing its employee numbers breach 1,000. Following a 20 per cent jump in revenues to €88.5 million in its financial year to last August, he has set his sights on hitting €100 million this year.

“It’s a different animal being a €100 million firm,” O’Brien says in an interview with The Irish Times in the firm’s boardroom in Dublin. “When I started off here, you’d be knocking on doors to get invites to tenders. Now large clients are coming to us and asking us to pitch. And if we’re not pitching, they’re wondering why.

“There is definitely an appetite for more choice amongst clients. The mandates we are being asked to pitch for now would have traditionally been the preserve of the Big Four.”

Forvis Mazars has some distance to go to catch up with Grant Thornton Ireland, fifth in the pecking order, which was forecast to deliver €330 million of revenues last year – or the Big Four, who each took in €558 million-€843 million last year. Unlike Forvis Mazars, however, the top five also include revenues from Northern Ireland.

O’Brien says the firm is only beginning to feel the benefits of a strategic partnership cemented in June 2024 – after two years of discussions – between Paris-headquartered Mazars, with offices in more than 100 countries and territories, and Forvis, the eighth-largest accounting firm in the US.

The old Forvis and Mazars businesses remain separate legal entities, now known as Forvis Mazars LLP and Forvis Mazars Group SC, respectively. The Irish practice has 45 partners, the vast majority of whom are equity partners in Forvis Mazars Group SC.

“For as long as I was a partner in Mazars, the US was a perennial strategic question. As Mazars got bigger, the requirement to have extensive coast-to-coast coverage in the US became greater,” he says.

This was especially the case when it came to servicing clients with a global presence, he says. Growing organically and striking a full-on merger deal each posed challenges. Forvis, meanwhile, had the opposite problem as it won global mandates, but didn’t have a European presence.

“We grew here over the years with a very, very small level of US business,” says O’Brien. “The opportunity for Ireland is massive. If we can get even a fraction of what other competitors have [from clients needing services on both sides of the Atlantic] it will really act as an accelerator. We’re excited about that.”

O’Brien, a native of Templeogue in southwest Dublin and son of a builder, spent his school holidays as a teenager working for his father and self-employed extended family, and became interested in accountancy after a sister went down that route.

He recalls working on a house roof with his father during the summer of 1993, after completing his Leaving Cert exams, when a call came from his career guidance teacher at Templeogue College saying he had got an interview for an on-the-job accountancy training position at a small accountancy firm, McGrath Comerford Rahill, on Baggot Street.

“I had to cobble together a suit and get myself into town for the interview that afternoon,” he says. Some 32 school leavers applied for positions and he was one of the two successful candidates.

The Institute of Chartered Accountants in Ireland (now Chartered Accountants Ireland) subsequently cut down on the so-called articles route into accountancy, where trainees in firms would study at night.

“I got experience in bookkeeping, accounting, audit, tax, company secretarial services, insolvency and more,” he says. “It was fantastic in terms of the spectrum I was exposed to. It’s something that trainees in large modern firms don’t get these days.”

Following a two-year stint with KPMG after he qualified, O’Brien joined Mazars – then a firm with 70-80 employees in the State – in its business advisory department in 2000. After initially focusing on audit work, he became a partner in transaction services for mergers and acquisitions (M&A), mainly working on due diligence for deals.

“That was in 2007. And I wasn’t even a year in the role before the world fell apart,” he says, referring to the financial crash. “I remember leaving for Christmas 2008 and another partner, Mark Mulcahy, and myself looking at each other, wondering where work was going to come from.”

Boom-era deals O’Brien worked on included ones carried out by construction services company Siteserv and The Irish Times’ purchase of property website MyHome.ie.

He would pivot into what became the new hot area: insolvency. Mazars was a very small practice at the time, with three or four people under an existing partner. “Our skill set from the transaction services side of things was very complementary in terms of working on business reviews, understanding numbers and workouts of trading businesses.

“It was a very difficult time. You came across a lot of people who had worked very hard all their lives and had run into trouble as the economy collapsed,” he says.

Like others, Mazars did a lot of work for the pillar banks, National Asset Management Agency (Nama), and funds that acquired portfolios from the banks.

The insolvency team grew to 65-70 at its peak, but has since fallen back to about 25, he says.

The crisis still shapes how he thinks and acts.

“It left me with learnings like the importance of timing and knowing when to get out of something, and the need to focus on cash – the lifeblood of a business – and managing

working capital so you don’t get caught,” he says. “I always say to people to seek early advice when there is a problem. That always gives you a better outcome. Otherwise, your options shrink by the week by delaying.”

The GAA fanatic – who played for Ballyboden St Enda’s in Dublin until he was 36 – became head of financial advisory at the firm in 2014, which includes M&A, transaction services and insolvency.

High-profile insolvency cases included his appointment as joint receiver over Apollo House in central Dublin in 2014, which became headline news around Christmas 2016, as they sought to regain possession of the property when it was taken over by activists and offered as accommodation to the homeless.

In late 2021 he was elected managing partner in Ireland. He was re-elected in September 2024 for a period that will stretch to late 2028. Revenues and staff have more than doubled in Ireland since he took charge.

In the hodgepodge of organisational structures of the top eight firms globally – with some, such as KPMG and BDO, pushing for regional clusters, albeit with different takes on what that actually means, and others, including firms within the Grant Thornton network, merging with the backing of private equity – the fully integrated non-US part of Forvis Mazars is “unique”, says O’Brien.

“We are one firm – integrated in every sense, from profit sharing to shared investments, IT systems and delivery platforms,” he says. “And aligned owners.”

The wider accounting sector has gone through a big shake-up in the past five years, driven by regulation and compliance costs and the need for big IT investment, including in artificial intelligence.

O’Brien sees consolidation continuing among small and medium-sized firms. Recent years have seen the likes of overseas firms such as Azets, Dains, DHJ and Moore Kingston Smith – many backed by private equity – acquire Irish businesses and use them as a platform for further deals.

At the other end of the market, he predicts “more clustering and global alignment” among network firms within the Big Four as multinational clients press for “consistency of services on a cross-border basis”.

O’Brien also sees more private equity involvement in the sector, even though he says it’s “difficult to achieve” true alignment between different types of owners.

Finally, he sees partner-led, integrated models like Forvis Mazars becoming more relevant for clients.

Asset management has become a big growth area within the firm’s financial services arm, as well as a data protection consultancy – as US firms struggle with the level of regulation in Europe.

Ireland is a big international hub for funds and serves as the European base of a slew of US tech giants.

Extending the firm’s regional offering was a priority when O’Brien took on the top job in 2021. It expanded into Cork three years later – adding to its offices in Dublin, Limerick and Galway – through a merger with long-established local firm James Byrne & Company.

The firm has also grown in recent years by “hiring partner teams that have a following in an area of high client demand”, especially in its fast-growing consulting business. It has also invested heavily in hiring senior figures in the audit part of the business.

Creeping past BDO Ireland last year to become the sixth-largest accountancy firm in the State by revenues in Finance Dublin’s annual ranking “was genuinely something that we are really proud of”, O’Brien says. The firm had been number seven for the previous decade, with “quite a gap” below BDO for much of that, he says.

Few industries are predicted to be reshaped by AI as much as professional services. O’Brien says his firm has had an AI and transformation group working in-house for the past decade on the implications of the anticipated revolution.

It has developed an internal AI tool – known as Gaia – to make some processes “less resource-intensive” and rolled out Microsoft Copilot, an AI assistant, across the business.

“We’ve spent a lot of time developing our AI policies – and making sure we had training so that everybody can understand when it can be used, what types of work it can be used on, and what sort of consents [are needed],” he says.

The consulting side of the business has also been helping clients “on their AI journey” in a “safe, controlled manner”, he says. “We’ve been working on advisory projects on supply chain management and deployed it in areas such as M&A due diligence,” he says. “I think it’s still early days, but there’s no doubt that AI is going to get a lot more powerful, sophisticated and business relevant.”

O’Brien says the “considered view” of Forvis Mazars’ AI gurus is that it will change work practices rather than replace humans. “I think we’ll end up with AI plus human, where AI does an amount of analytical work and processing, but then the human comes in at the end to interpret it,” he says.

Many see that scenario still requiring far fewer humans. “Or doing different types of work,” offers O’Brien.

“One of the challenges for our profession is, how do you train up the next generation of partners where they may have a training experience that won’t involve a lot of the fundamentals [of the past],” he says.

“That really needs a considered response from the industry and third-level institutions.”

But while many in the sector have been cutting back on graduate hiring in recent years as AI does away with entry-level jobs, O’Brien says Forvis Mazars brought in a record 100 people straight from college in October – up from 90 for the previous year. “We’ve had double-digit [revenue] growth for a number of years, so we’ve had to staff up to meet client demand. But it’s still a highly competitive market.”

O’Brien says the firm has had to pay extra attention to junior staff hired during the pandemic. “Many still have never really worked exclusively in the office. They’re not listening to phone calls in the office and learning from more senior people on how to engage with clients,” he says.

“The learning and development work has to be much more than technical with them.”

He says Forvis Mazars’ hybrid working model in Ireland remains “quite flexible and departmental-specific”. Some areas might require staff to be in the office for five days over two weeks, while others might just be one day every fortnight, he says.

“If you look at the Irish economy over the last nine years and all the individual shocks – from Brexit to Covid, the Ukraine war, inflation, interest rates and tariffs – it’s proven itself to be remarkably resilient,” he says.

While he notes that Ireland has long played a role of being a bridge between Europe and the US, “ultimately we’re going to have to come down on one side” as the traditional rules of engagement have changed. US president Donald Trump doesn’t even need to be mentioned.

As with the early days of Brexit, the firm is seeking a lot of larger corporates deferring or suspending investment “until things become clearer”, he says. “We’re not seeing the [economic] impact now, but we potentially will down the line.”

CV

Name: Tom O’Brien

Age: 49

Position: Managing partner of Forvis Mazars in Ireland

Lives: Griffith Avenue, Dublin

Family: Married to Tracy, with two sons, Cian (17) and Conor (14)

Hobbies: All things GAA-related

Something you might expect: “As football was a big part of my life for so many years, I firmly believe in the power of teamwork.”

Something that might surprise: “Unlike most of my contemporaries and friends, I didn’t go to college. I joined an accountancy firm after my Leaving Cert and spent three years completing my professional exams at night.”