Retainer vs Hourly Rates: Interim FD Contracts

Interim Finance Director contracts get compared to hourly consulting arrangements more often than the UK market actually supports. In practice, hourly billing is rare at FD level — senior finance leadership isn’t naturally divisible into tracked hourly increments the way some professional services work is, and most clients want a defined day-a-week commitment rather than an open-ended hourly meter running. The real choice UK businesses face is between a day rate structure and a retainer, and the two suit genuinely different engagement shapes.

Why Day Rate, Not Hourly, Is the UK Norm

Interim FD work is almost always structured around days worked, not hours logged. A handful of reasons this has become the standard:

• The work doesn’t decompose well into billable hours. An interim FD’s value comes from ongoing presence, judgement and relationship continuity with the CEO, board and finance team — not discrete, separately-billable tasks.
• Clients want predictable commitment, not a running total. A defined “two days a week” or “three days a week” arrangement is easier for a business to plan around than an hourly bill that could vary month to month.
• Administrative overhead. Hourly billing at FD level would require detailed time-tracking that most interim FDs (and most clients) find disproportionate to the value of the work.

Day Rate: The Default Structure

Under a day rate arrangement, the interim FD is paid a fixed amount per day worked, typically against an agreed minimum commitment — for example, two or three days a week for the duration of the engagement. This is the structure behind the large majority of UK interim FD placements, because it maps cleanly onto how the role is actually delivered: defined days on-site or working the business, clear cost per day, and straightforward scaling up or down as the engagement’s needs change.

Day rate suits almost any interim FD brief — cover for an absence, a defined project (fundraise, systems implementation, turnaround), or an open-ended appointment while a permanent search runs in parallel.

Retainer: The Less Common Alternative

A retainer — a fixed monthly fee for a defined scope of ongoing availability, rather than payment per day worked — is genuinely less common in the UK interim FD market, but it does have a place. It tends to suit lighter-touch, advisory-style arrangements: an interim FD providing occasional strategic input and availability for a business that doesn’t need days-a-week presence, sitting closer to a fractional or NED-adjacent role than a full interim appointment.

The trade-off is straightforward: a retainer gives the client budget certainty and the FD guaranteed income regardless of exact hours, but it works less well where the actual workload is genuinely variable — a business in crisis needing intensive support one month and comparatively little the next is usually better served by day rate, which flexes with actual need.

The Question That Actually Matters More: IR35

Whichever fee structure is used, the more consequential decision in a UK interim FD engagement is usually the IR35 / off-payroll working status determination — something the retainer-vs-hourly framing often misses entirely. Since the 2021 reforms, medium and large private-sector businesses are responsible for determining whether an interim FD engaged through a personal service company falls inside or outside IR35, and getting this wrong carries real tax and penalty risk for the engaging business, not just the contractor.

This affects contract structure directly: engagements with genuine autonomy over how the work is delivered, the ability to send a substitute, and no day-to-day supervision in the manner of an employee tend to support an outside-IR35 determination. A status assessment should be carried out and documented — via HMRC’s Check Employment Status for Tax (CEST) tool or independent advice — before the engagement starts, not after HMRC asks.

Negotiating the Terms That Matter

• Minimum days per week or month, and how much notice either side needs to change it
• Contract length and renewal or exit terms — most interim engagements run in defined blocks (three months, six months) with a review point rather than an indefinite open-ended arrangement
• IR35 status determination, agreed and documented before the engagement starts
• Expenses — travel, subsistence and any other costs, and whether they sit inside or outside the day rate
• Scope — what the interim FD is and isn’t responsible for, to avoid the role quietly expanding beyond the original brief

How FD Capital Structures These Engagements

FD Capital places interim FDs and CFOs across the UK on day-rate contracts as standard, with IR35 status addressed as part of the placement process rather than left to be resolved after the engagement starts. If you’re weighing up structure for an interim FD appointment — or need one placed — we’re happy to talk through what fits your specific situation.

References

• HMRC / gov.uk — Check Employment Status for Tax (CEST)
• HMRC / gov.uk — Understanding Off-Payroll Working (IR35)

This article is provided for general information purposes and does not constitute tax or legal advice. IR35 status should be assessed on the specific facts of each engagement, ideally with professional advice. FD Capital Recruitment Ltd is registered at Companies House (no. 13329383) and is operated by an ICAEW-registered practice.

Adrian Lawrence

Adrian Lawrence FCA is the founder of FD Capital and a Fellow of the Institute of Chartered Accountants in England and Wales (ICAEW). He holds a BSc from Queen Mary College, University of London, and has over 25 years of experience as a Chartered Accountant and finance leader working with private, PE-backed and owner-managed businesses across the UK. He founded FD Capital to connect growing businesses with the Finance Directors and CFOs they need to scale — and personally interviews candidates for senior finance appointments.