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The team you trust, now with even more to offer

Riordan O’Sullivan & Co is now a part of Simmons Gainsford

What’s happening?

We have joined forces

We are pleased to share that Riordan O’Sullivan & Co has joined forces with Simmons Gainsford, a move that brings together two firms with a shared commitment to client service, specialist expertise, and long-standing relationships.

While the name may be changing, the people and service you know remain the same – now with the added benefit of access to a broader network of knowledge and resources.

  • Familiar Faces
    Your usual contacts at Riordan O’Sullivan & Co are still here and continuing to support you.
  • Expanded Services
    You’ll now also have access to Simmons Gainsford’s full range of services including tax, audit, advisory, outsourced finance, payroll, financial services, and more.
  • Seamless solutions
    This integration enables us to support your needs even more effectively, across every stage of your business or personal financial journey.

About Simmons Gainsford

The Obvious Choice for Quality Advice and Service

First established in 1948, Simmons Gainsford is a multidisciplinary firm of chartered accountants and business advisers. Our main office is in Central London, with additional offices in Sussex and Gibraltar. Our size, structure, and resources enable us to provide the full range of services and technical expertise, but with the personal touch that comes from a high level of partner engagement.

In December 2023, Simmons Gainsford joined the Sumer Group, the UK and Ireland’s leading mid-market accountancy practice delivering professional support to small and medium-sized enterprises (SMEs) across England, Scotland, and Northern Ireland. It is a top 15 UK accountancy practice consisting of over 2,500 people across more than 50 UK offices on a mission to champion SME businesses and offer local delivery supported by national expertise.

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What the team says

Our Combined Strength

“We are delighted to welcome Riordan O’Sullivan & Co to our group. Their excellent reputation and strong client relationships perfectly complement our mission to champion SMEs throughout the UK. This merger represents another significant step in our ambitious growth strategy.”

Darren Hersey
Senior Partner of Simmons Gainsford

“Joining Simmons Gainsford marks an exciting new chapter for our firm. Our clients will benefit from enhanced service capabilities while maintaining the hands-on personal relationships we know they expect and value. We’re proud to join an organisation that shares our commitment to supporting SME businesses and the communities they serve.”

Kumar Perumal
Client Director, Simmons Gainsford incorporating Riordan O’Sullivan & Co

Sumer line

They said it best

Linda Yi
Financial Controller, BenQ UK Limited

“Simmons Gainsford have been our trusted advisers since our incorporation in 1997, and their support has been integral to our success. They handle every aspect of our financial and compliance needs, including accounts preparation, audit, corporation tax compliance, payroll, and VAT. Their comprehensive approach gives us peace of mind, knowing that every detail is managed with precision and care. In the past, they've also expertly guided us through HMRC’s complex periodic audit, ensuring we navigated any challenges smoothly. Chris Cheung and Shilen Manek’s dedication and in-depth knowledge make Simmons Gainsford an essential part of our business operations. We couldn't recommend them more highly."

Ian Scott
Finance Director, The Evolve Group

"Simmons Gainsford has been a trusted partner of The Evolve Group for nearly a decade. Their team has provided us with invaluable support over the years - from audit services to accountancy and tax advice - always combining technical expertise with a deep understanding of our business. During the challenges of the Covid period, their guidance around carrying back losses to secure tax refunds was particularly impactful. We greatly value the relationship and the continuity they've provided as our business has grown and evolved.”

Jon Noble
Chairman, RG Property Group

“Simmons Gainsford have been our accountants since the company was formed in 1989. During this period, they have seen us grow from a small company to one that has a turnover in excess of £200m. They were heavily involved in a management buyout and subsequent change of ownership from a joint venture between a partnership and a PLC to a privately owned company. Simmons Gainsford have always been by our side throughout this 30-year period and the partners have been an integral part of many key decisions the company has made. We have a great relationship with the partners, they not only look after the companies’ accounts but also all our individual financial matters. I would have no hesitation in recommending the company to anyone, I really do feel we have the best.”

Emma Cullen
Chief Operating Officer, Fiera Real Estate UK Limited

“We have worked with Simmons Gainsford since the inception of our business and our partnership has been grown over 25 years plus. I see SG as a key business partner, working closely with them at both an operational and strategic level. Our work is both complex and high volume and they have an exceptional team that delivers within very tight deadlines.”

Charles Bernitz
Founder and Former Owner, Digital Gaming Corporation

“I've worked with Simmons Gainsford for many years, and they’ve been a trusted adviser throughout my career. When I founded Digital Gaming Corporation UK in 2013, we turned to SG for their expertise and strategic guidance. From UK audit and tax to international structuring, they worked seamlessly with our US advisers and supported us every step of the way. As we expanded into multiple US states and were acquired by Betway Group, SG remained a constant, offering practical, forward-thinking advice. They’re more than auditors—they’re true partners. I’d highly recommend them to any business in the online gaming sector.”

Meloney Wiltshire-Payne
CEO, Corporate Media Partners Limited

“Our business has changed significantly over the years having faced numerous challenges, during these times Simmons Gainsford have always been very supportive. Their team relates well to us, and they take the time to understand the business and its journey. Our shareholders like to try out different ideas, which the SG team always take in their stride, they ask the relevant questions and are not afraid to challenge or disagree, not least because their technical knowledge is second to none, all the while remaining focused on the broader objectives of the directors and shareholders. The audit team on the ground is also very good and communicative, they always take the time to listen, explain and understand. And having continuity with the team, which is an important factor for me, helps to ensure that we have a very good two-way working relationship. All in all, we really do feel as though we’re in safe hands.”

Brian Cassidy
Chief Financial Officer, Brooklyn Travel Limited

“Our relationship with Simmons Gainsford dates back to 2018, having initially engaged them to carry out the audit of our subsidiary, Stewart Travel Limited. We extended their services across the wider Brooklyn Travel Group following our formation in 2019. They provide us with comprehensive support across audit, tax, and accounts preparation, along with valuable advisory input when needed. Their team works closely and effectively with our finance functions across multiple locations, including the UK and Finland, demonstrating strong communication, consistency, and flexibility. One of the key strengths of Simmons Gainsford is their ability to deliver our group audit to tight regulatory deadlines. With a December year end and a requirement to submit audited accounts to the Civil Aviation Authority (CAA) by the end of March each year, timing is critical. We value their technical expertise, their understanding of the travel industry, and the collaborative way they work with our team.”

FAQs

Why have Simmons Gainsford, part of the Sumer Group acquired Riordan O’Sullivan & Co?

This partnership brings together two thriving businesses with complementary strengths and a shared purpose and values. Riordan O'Sullivan & Co’s excellent reputation and strong presence in North London enhances the Sumer Group's ability to serve clients across the UK with local expertise backed by national resources.

Will there be any changes to client service teams?

Clients will continue working with the same trusted professionals they know. Riordan O'Sullivan & Co team will remain in place, now with access to additional resources, specialised expertise, and technology to enhance client service.

Will Riordan O’Sullivan & Co be changing its name?

Sumer adopts a regional brand approach and following the deal we have become part of the enlarged regional practice within London. This will mean after a short transition period we will adopt the Simmons Gainsford name.

How does this affect Riordan O’Sullivan & Co's operations?

Day-to-day operations will continue smoothly. The local leadership team remains in place and will continue to operate from its headquarters at: 38-40 Chamberlayne Rd, London NW10 3JE. Over time, clients will benefit from enhanced capabilities and access to specialised services through Sumer Group's national network.

Does this partnership signal further expansion for Simmons Gainsford, part of the Group in London?

Simmons Gainsford is committed to strategic growth in the region. We continue to seek opportunities to enhance our ability to serve SME businesses throughout the country.

How does this merger fit into the Sumer Group's overall strategy?

This partnership aligns perfectly with the Sumer Group's strategy of investing in exceptional firms that share our commitment to championing SME businesses. With backing from Penta Capital and BlackRock, the Sumer Group aims to grow rapidly over the coming years through strategic partnerships with leading regional firms like Riordan O'Sullivan & Co.

Contact us

London Office
Tel: 020 7447 9000
Email:mail@sgllp.co.uk

Uckfield Office
Tel: 01825 746 888
Email:mail@sgllp.co.uk

Gibraltar Office
Tel: +350 2005 9753
Email:mail@sgllp.gi

North London Office
Tel: 020 8969 9411
Email:mail@sgllp.co.uk

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