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Mishcon advises on partnership between Onside Accounting Limited, Onside Tax Limited and Multiplier Holdings

Posted on8 September 2025

Mishcon de Reya's Corporate team has acted for Martin Brennan and Ryan Snape, in connection with the partnership of Onside Accounting Limited and Onside Tax Limited with Multiplier Holdings.  

Onside provide start-up focused accounting, tax and finance services to support early-stage businesses through their growth journey, and Multiplier are an AI-native professional services company. Backed my Multiplier, the Onside business will benefit from custom built technology, to further improve Onside's innovative and sector-unique offering to its clients. Martin and Ryan will continue their pivotal roles with the businesses post-completion, benefitting from a partnership with Multiplier to further build on the immense success of the business to date.   

The team at Mishcon de Reya was led by Partner, Charie Fletcher with support from Danny Whittaker (Corporate Associate). The wider Mishcon de Reya team included advice from Stephen Elhabbal (Tax Managing Associate), Margarita Elia (Employment Consultant), India Coultas (Employment Associate), and Emily Francis (Data Protection Managing Associate).  

Charlie Fletcher, Partner at Mishcon, commented: "This deal represents the latest shifting of the guard towards an AI-enabled future which promises a next level of service, advice and value. These are extremely exciting times for the Onside team who, with the backing of Multiplier, will be leading the charge as their industry is reinvented through technology. We are proud to have delivered this game-changing transaction." 

Danny Whittaker, Associate at Mishcon, commented: "We are really pleased to have secured another successful partnership for one of our founder managed clients. This transaction is wholly reflective of the exceptional work of Martin, Ryan and the Onside team – taking Onside from start-up to one of the fastest growing accountancy / tax service providers in the UK is a monumental achievement and it is a real testament to the entirety of the Onside Team. It was an absolute pleasure working with Martin and Ryan, and we can't wait to see where this new partnership takes the Onside business. We wish them, the Onside Team and Multiplier Holdings every success." 

Martin Brennan, CEO of Onside Accounting, commented: "This partnership marks a super exciting next chapter for Onside. With Multiplier’s AI-native technology and our team’s expertise, we have the chance to elevate client service to a new standard while freeing our people to focus on the work that really matters. After 15 years in practice leadership, I’ve never been more excited about the opportunities ahead. This strategic partnership protects everything we’ve built and sets us up to achieve far more than we could do alone. It was a genuine pleasure working with the Mishcon team, who were quick, responsive and available throughout – their support made it possible to complete this transaction in just four weeks" 

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