Financial Controller | AI SaaS Scale-up

Interim Financial Controller | AI SaaS Scale-up | London

Harmonic are delighted to be partnering with a founder-led AI SaaS business in their search for an Interim Financial Controller. The business built its own AI platform which it sells to UK service businesses. It launched at the start of 2026 and has grown to c.£1m in annual revenue and a team of eight in its first year. The business is bootstrapped by the founder, a second-time operator who has an excellent track record of scaling and exiting technology businesses. The founder now needs someone embedded in the business to run the finance day to day and manage his wider portfolio.

The Role

This is a full-time interim role, taking over from the current finance lead, with a handover in early December. The brief is to run the core finance operation for the trading business: management accounts, payroll, AP/AR, VAT and reconciliations, as well as supporting the founder with the finance matters of their private office and investments. The founder is thinking about a permanent founder's or family office role, and this person will help inform what that looks like.

Key Responsibilities

• Produce monthly management accounts
• Run payroll, invoicing, supplier payments and credit control
• Handle contracts, paperwork and office-related financial admin
• Advise the founder on funding new ventures and allocating capital across the portfolio
• Help design the longer-term finance structure, including the full-time hire into the operating business
• Stay hands-on with the detail, including the admin that comes with a multi-asset structure

What We Need to See (Essential)

• Part qualified, finalist or qualified (CIMA, ACCA or ACA)
• Operating finance experience in a start-up or scale-up
• Experience in an online or digital business; SaaS or recurring revenue preferred
• Hands-on and comfortable running finance on your own

What We'd Like to See (Bonus)

• Previous experience within a family office, founder's office, or PE/VC fund finance
• Experience working directly with a founder or principal

Day Rate:£500-650 per day

Location: London, mix of office and remote to be agreed

Contract: Full-time, 6 months (open to part-time fractional candidates)

Start Date: ASAP

At Harmonic, we are dedicated to fostering an inclusive and equitable workplace. We actively welcome applications from individuals of all backgrounds and assure you that every candidate will be thoughtfully considered for the roles we represent, without regard to race, religion, gender expression, disability, or sexual orientation.