Assistant Management Accountant

Company: On Device
Position: Assistant Management Accountant
Location: London Office/Hybrid
Work Pattern: Monday to Friday 9.00am - 6.00pm

On Device is a Brand Lift Measurement company for advertisers, planners and publishers. Our cross-media measurement system makes every aspect of brand advertising accountable through dissecting campaign performance to reveal the truth on brand advertising effectiveness. Partnering with leading brands, ad agencies and media owners, the company has earned recognition through various awards for its exceptional work, including Best Companies to Work for in 2023 and 2024.

On Device Research is looking for an Assistant Management Accountant to join a small, supportive finance team. The team consists of the Finance Director, this role, and a Fractional CFO who works one day per week. You will report directly to the Finance Director.

This is a mixed role in a small team. In the first 3–6 months you will spend roughly half your time on AP, AR, the accounts inbox and bank reconciliations. The Finance Director continues to produce the monthly accounts during this period while you learn the business and the ledgers. Over the following months, as transactional work is automated, the time spent on Finance Assistant work drops, with you taking on more of the month-end production.

It is a great opportunity for someone studying CIMA or ACCA — at any stage from just starting out to part-qualified — who wants real ownership of ledger work, exposure to month end, and the chance to grow into management accounts production. We will fully support your continued study.

• Supporting the Finance Director at month end with reconciliations, journals, and inputs. The FD will continue to produce the monthly accounts for the first 3–6 months while you settle in.
• Posting standard month-end journals under FD direction: accruals, prepayments, depreciation, payroll, and similar.
• Owning balance sheet reconciliations (control accounts, accruals, prepayments) for FD review.
• Preparing the monthly sales commissions report for FD review and payment.
• Over time, taking on more of the month-end production currently done by the FD as your confidence and the teams automation grow.

• Maintaining a small set of Excel models, including a cash flow tracker, aged debt analysis, and the weekly AR/AP reports.
• Producing useful weekly AR and AP reports the FD can act on (cash impact, ageing, queries, risk items).
• Supporting ad-hoc commercial analysis for the FD and Fractional CFO.
• Helping respond to budget holder finance queries with FD oversight.

• Owning AR end-to-end: raising sales invoices in Xero, allocating receipts, credit control, and aged debt management.
• Owning AP end-to-end: adding supplier invoices to Xero with clean coding and supplier setup, and preparing payment runs for FD approval.
• Managing the shared accounts inbox for AR and AP queries.

• Owning Xero bank reconciliations end-to-end, including managing the auto-rec tool and applying judgement on coding and exceptions.

• Helping to tighten day-to-day finance controls (approvals, coding, supplier setup).
• Leading the automation of transactional and reporting work — finding ways to reduce manual effort and free time for management accounts work.
• Identifying and leading improvements to Xero workflows and reconciliations.
• Documenting finance processes so the team has a single source of truth.

• Studying CIMA or ACCA — any stage from just starting out to part-qualified. We will fully support your continued study.
• 1–3 years experience…