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Mark O'Sullivan, Director


Mark is the Head of R&D Technical Services within BDO's R&D Tax Services department. Mark has significant experience working with companies across all sectors, having focused on R&D tax credit practices in both KPMG and BDO since 2011. During this time Mark has been involved in compiling hundreds of R&D tax credit claims and qualifying over 1,000 projects. This includes compiling and defending a number of the largest R&D tax credit claims made in the country to date.


As head of R&D Technical Services, Mark liaises with clients’ technical personnel to establish what qualifying R&D activities were undertaken in the relevant period of the claim and determines, from a technical perspective, what R&D activities would be considered potentially eligible for the purposes of the R&D tax credit regime.

Mark has extensive Revenue audit experience having assisted numerous clients in engagements with Revenue. To date, Mark has successfully qualified and defended numerous R&D tax credit claims made, from a technical perspective. This is largely based on the knowledge set and methodology utilised coupled with the due diligence placed on the review process undertaken with clients prior to inclusion of projects in a claim.

Mark is a member of Engineers Ireland and has professional qualifications in Medical Physics, Mechanical Engineering, Manufacturing & Design Engineering and Computer Science.

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