Growth Tax Manager

Reporting to: Head of Tax - Onside Tax

Salary: £45,000 to £60,000 depending on experience and qualifications

Location: Remote - working from home in the UK

The UK tech sector is growing rapidly and becoming an increasingly important part of the economy. At Onside, we’ve built a genuinely differentiated way to support tech-led businesses, combining premium client service with modern systems, automation, and commercial thinking.

We believe the strongest professional services firms of the future will be technology-led by design, with automation and data removing low-value work so people can focus on judgment, relationships, and impact. Onside is being built deliberately around that belief. We are not just users of technology; we are, in part, a technology company ourselves, backed by Multiplier, a San Francisco–based, AI-native professional services company designed to transform our industry.

The Tax Manager will take ownership of Onside’s wider tax offering for fast-growing, VC-backed technology businesses, acting as a trusted lead on day-to-day delivery while working closely with the Head of Tax and Managing Director. The role centers on transfer pricing, EMI, EIS/SEIS, VAT, and other tax matters that arise as clients grow, and is well suited to someone who works well with autonomy, enjoys responsibility, builds strong client relationships, and thrives in a fast-paced, tech-led environment.

This is a fast-paced role with high standards. We value accuracy, curiosity, and ownership and there is a clear progression path for people who demonstrate energy and capability. It’s an opportunity to learn how modern, technology-led finance teams really operate and build a strong platform for your continued career.

Applicants must be confident managing priorities, delivering work independently, and collaborating effectively in a remote environment, including throughout their initial training and induction period.

This role requires substantial experience of long-term homeworking within a UK accounting practice. Remote working experience gained solely during Covid-19 restrictions will not be considered. Applicants from formal hybrid arrangements may be considered, provided homeworking was a long-term, contracted arrangement involving typically two to three days per week working from home.

Key Responsibilities

The key responsibilities of the Tax Manager are:

• Taking ownership of a portfolio of tax work for start-up and scale-up clients, and acting as a key point of contact on the matters they lead.
• Preparing and delivering tax advice on transfer pricing matters, including scoping, technical analysis, report writing, and implementation support.
• Preparing EMI valuation reports and supporting clients with EMI and ERS advice/compliance, including HMRC submissions and related advisory work.
• Preparing EIS1/SEIS1 compliance filings and supporting advance assurance applications.
• Advising clients on VAT matters, including UK and cross-border issues arising as businesses grow and expand into other jurisdictions.
• Supporting clients with ad hoc tax advisory projects, including restructurings, remuneration planning, employment-related tax issues, and wider corporate tax matters.
• Reviewing Corporation Tax returns and associated computations on an ad hoc basis, working alongside the accounts team who manage preparation, and providing technical input to ensure accuracy and identify risks or planning opportunities.
• Undertaking tax research, reviewing legislation and HMRC guidance, and forming well-reasoned conclusions based on independent analysis.
• Producing high-quality written advice, reports, and technical correspondence for clients and internal use.
• Leading and contributing to client calls and meetings, explaining technical tax issues in a clear, practical, and commercial way.
• Building strong client relationships, supporting efficient delivery, and identifying improvements in processes, technology, automation, and wider commercial opportunities across the tax function.