By Laura Allen, Founder & Managing Partner, The Fractional Agency
If you’re a senior executive exploring life outside a permanent role, you’ve probably come across both terms. Fractional. Interim. They’re used interchangeably in job posts, on LinkedIn, and sometimes even by the recruiters placing the roles. But they are not the same thing, and understanding the difference isn’t just a matter of semantics. It affects how you structure your work, how you get paid, how you’re taxed, and how you build a career that actually compounds over time.
This is especially true if you’re working in M&A and PE-backed environments, where the distinction shapes the entire nature of the engagement.
An interim executive is typically brought in full-time, or close to it, for a defined period. The engagement has a clear start and end date. The business usually needs someone to fill a leadership gap, manage a crisis, lead a specific transformation, or bridge between permanent hires. It’s intensive, time-bound, and the expectation is full-time presence and focus.
A fractional executive works with a business on a part-time basis, usually structured as a set number of days per week or a monthly retainer. The key difference is that a fractional works across multiple clients simultaneously. You’re not a temporary full-timer. You’re a permanent part-timer, embedded in the leadership team but bringing the breadth of experience that comes from working across several businesses simultaneously.
Both models involve senior, experienced leaders. Both can operate at C-suite level. Both are legitimate and in demand. But they serve different needs, carry different commercial structures, and have very different implications for how you build your practice.
With interim, the client is buying your time, almost exclusively. You’re expected to be there, present, responsive, often on-site. The engagement is usually structured on a day rate, and the client expects something close to the commitment of a permanent employee for the duration.
With fractional, the client is buying your expertise and your outcomes, not your hours. You might work two days a week with one client and two days a week with another. Your retainer is based on a defined scope and a defined time commitment, and what matters is whether you’re moving the business forward, not whether you’re in the building on a Tuesday.
That shift from selling time to selling impact is one of the most important mental adjustments that experienced executives need to make when moving into fractional work. It’s also one of the most commercially liberating, once you’ve made it.
This is where a lot of people get confused, and it’s worth being clear about it.
IR35 is a set of HMRC tax rules designed to catch what they call “disguised employees”. Contractors who operate through a limited company but work in a way that’s functionally identical to being on the payroll. If you fall inside IR35, you get taxed like an employee. If you fall outside it, you’re treated as a genuine contractor and handle your own tax through your company.
The three factors HMRC looks at are control (who directs your work and how), substitution (can you send someone else to do the work if needed), and mutuality of obligation (is the client obligated to offer you work, and are you obligated to accept it).
Here’s why this matters for the fractional vs interim question. Interim engagements, particularly full-time ones with high control and no substitution rights, carry a higher IR35 risk. A fractional arrangement, properly structured, is generally more defensible as outside IR35 because you retain genuine independence, you work across multiple clients, and your contract is based on outcomes rather than hours.
That said, the rules are not simple, and they changed significantly in 2025. For any medium or large private sector business (broadly: turnover over £15m, balance sheet over £7.5m, or more than 50 employees), the client determines your IR35 status, not you. For smaller businesses, you assess your own status.
The practical upshot: always have your contract reviewed for IR35 compliance before you start, regardless of which model you’re operating under. Never assume. The structure of the engagement, the wording of the contract, and the reality of how you work all factor into the determination. Get proper advice from a company like https://www.goqdos.com
Most interim roles are priced on a day rate. Most fractional engagements run on a monthly retainer, which is effectively a hybrid model: a fixed fee for a guaranteed number of days per month.
The retainer model is generally preferable in fractional work, for a few reasons. It gives you predictable income. It gives the client predictable access to your time. And it shifts the conversation away from hours worked and towards the ongoing value you’re delivering. A client on a retainer is in a relationship with you. A client on a day rate is managing a cost.
How you set that rate matters. As a self-employed executive, you’re covering taxes, National Insurance, pension, insurance, equipment, and all the non-billable time that comes with running your own practice. A useful starting point: take the gross salary equivalent of your role, apply a 1.3x to 1.5x uplift to account for the real costs of self-employment, then divide by your realistic number of billable days in a year (usually around 220, once you account for holidays, admin, and non-billable time). That gives you a baseline day rate. For senior M&A fractionals in the UK, typical day rates sit between £800 and £1,500, depending on role, sector, and the complexity of the mandate.
Whatever the structure, never start an engagement without a signed contract. The contract should define scope of work clearly to prevent scope creep, set payment terms and what happens if payment is late, include a termination clause for both parties, and address confidentiality and IP. These aren’t bureaucratic formalities. They’re what protect you when a client relationship changes or ends unexpectedly. If you need help with this, we recommend you speak to TFA’s trusted partner https://new-legal.com/.
In deal environments, the lines can blur in ways that a simple definition doesn’t capture. Take a CFO brought in post-acquisition. The first ninety days might look close to full-time, establishing financial controls, getting reporting PE-ready, and managing the data room hangover. But once that foundation is in place, the same person transitions into two or three days a week. That’s not interim followed by fractional. That’s one fractional engagement with a variable intensity curve built into the contract from the start.
Or consider a Chief People Officer engaged during a carve-out. The people workstream in a carve-out is intense and deadline-driven. TUPE obligations, org design, leadership restructuring. A standard fractional model of fixed days per week doesn’t work. But neither does a traditional interim, because the CPO also needs to be thinking twelve months ahead about culture, retention and capability building in the new entity. The engagement needs elements of both: defined project milestones and ongoing strategic presence.
This is where TFA spends a lot of its time: working out which model is right for which phase, and making sure both the business and the candidate are set up for an engagement that actually delivers. Some clients come to us looking for a fractional and end up wanting to offer an in-house interim placement. Anything is possible.
As a candidate, being able to articulate clearly which model you’re suited for, under what conditions, and why, is part of what separates the executives who build strong reputations in this space from those who drift between engagements without a clear positioning.
That depends on what you’re optimising for.
Interim suits you if you want full-time intensity, a defined mission, and a clean exit. You go in, deliver, leave. It’s high focus, relatively straightforward commercially, and a well-understood model for most businesses and PE firms.
Fractional suits you if you want to work across multiple clients simultaneously, build a portfolio career with compounding reputation, and shift from selling time to selling expertise. It requires more commercial discipline upfront around positioning, pipeline, and how you structure your engagements. But the ceiling is higher and the autonomy is greater.
For many senior executives with M&A backgrounds, the answer over time is both. You might take an intensive interim mandate to establish yourself with a new PE firm, then transition into a fractional relationship with the portfolio company. Or you might run two or three fractional mandates in parallel while staying open to a focused interim piece when the right one comes along.
The point is to know which model you’re in, structure it properly, and never conflate the two – either in how you present yourself to clients, or in how you set up the commercial and contractual terms.
Laura Allen is the Founder and Managing Partner of The Fractional Agency, a specialist M&A fractional C-suite platform connecting PE-backed and mid-market businesses with vetted fractional leaders across the deal lifecycle.
If you’re weighing up which model is right for you and want to understand what mandates TFA is currently placing, get in touch here.
