The Complete Guide to
Fractional CFO Services in the UK

What is a Fractional CFO?

A fractional CFO is a senior finance executive who provides part-time strategic financial leadership to companies that need the judgement of a Chief Financial Officer without the cost of a full-time hire.

The key word is strategic. A fractional CFO is not a bookkeeper and not a replacement for your accountant. Bookkeeping and accounting record what has already happened; a fractional CFO is concerned with what happens next — how long your cash lasts, what your next round needs to look like, whether your pricing supports the business you are building, and what the board should be told and when.

Like a fractional CTO, a fractional CFO is embedded rather than advisory-only. They own the financial model, sit in board meetings, field investor questions, and take accountability for the quality of your numbers — typically for one to three days a week rather than five.

The model has become a natural fit for UK startups between pre-seed and Series A: the financial workload at that stage is genuinely executive-level, but it is not yet a five-day-a-week job. Fractional finance leadership is one of the two executive seats Codenest provides — you can read exactly what an engagement includes on our Fractional CFO services page.

What Does a Fractional CFO Do?

The responsibilities of a fractional CFO flex with your stage and situation, but for a pre-seed to Series A startup they typically cover five areas:

Financial Modelling & FP&A

• Building and maintaining a three-statement financial model founders can actually use
• Budgeting, and monthly budget-versus-actuals reviews
• Scenario and sensitivity analysis — what happens if sales slip a quarter, or a hire is delayed
• Defining the KPIs that matter for your business model, and reporting them consistently
• Modelling the cash impact of hiring plans and major spend decisions before they are made

Related reading: Financial modelling for seed-stage startups →

Cash & Runway Management

• A 13-week rolling cash flow, so short-term cash is never a surprise
• Burn tracking and runway scenarios under different growth and spend assumptions
• Working-capital management — debtor chasing, creditor terms, VAT timing
• Cost reviews and supplier renegotiation when runway needs extending

Fundraising Support & Data Rooms

• Sizing and timing the raise against your milestones and runway
• Preparing a model that survives investor diligence, with assumptions you can defend
• Building and managing the data room before investors ask for it
• Supporting term-sheet review and cap-table modelling alongside your lawyers
• Preparing founders for the financial questions investors will ask

Board & Investor Reporting

• A monthly management accounts and KPI pack, produced on a reliable rhythm
• Owning the financial section of the board pack — and the narrative around the numbers
• Regular investor updates that build confidence between rounds
• Grant, covenant or R&D-claim reporting where relevant

Unit Economics & Pricing

• Customer acquisition cost, lifetime value and payback period — measured, not guessed
• Contribution margin by product, plan or customer segment
• Pricing structure and pricing-change analysis grounded in margin and willingness to pay
• Discounting policy, so sales flexibility does not quietly erode the model

When Should You Hire a Fractional CFO?

Most founders bring in a fractional CFO in response to one of five triggers:

You're Preparing to Raise

This is the most common trigger, and the one with the clearest payoff. Investors will diligence your numbers: the model, the assumptions behind it, historical performance and the data room. A fractional CFO gets all of that investor-ready — ideally starting three to six months before you go out, so the numbers shape the raise rather than scramble after it.

You've Just Closed a Round

New capital demands new discipline. The plan you pitched needs to become a budget; the investors who wired the money expect regular reporting; and spend decisions now carry someone else's money. A fractional CFO turns post-raise good intentions into a working financial operating rhythm.

Runway Is Under Pressure

When cash is tight, precision matters. A fractional CFO replaces a vague sense of "about a year left" with a 13-week cash flow, runway scenarios, and a clear-eyed view of which costs to cut, defer or renegotiate — and how those choices trade off against growth.

Not sure where you stand? Use our free runway calculator →

Board Reporting Is Getting Demanding

Once institutional investors join your cap table, expectations change. Monthly management accounts, a proper board pack, and answers that hold up to scrutiny become the baseline. A fractional CFO takes that burden off the founders and raises the standard at the same time.

You're Making Pricing and Unit-Economics Decisions

Pricing changes, discount policies, and which customers to pursue are finance questions as much as commercial ones. If those calls are being made on instinct rather than margin analysis, a fractional CFO pays for themselves quickly.

How Much Does a Fractional CFO Cost?

UK fractional CFO pricing varies with experience, sector and — above all — intensity. Most engagements fall roughly between £2,000 and £12,000 per month:

Codenest Fractional CFO engagements start from £2,500 per month — see the Fractional CFO services page for what each engagement includes.

Cost Comparison: Fractional vs Full-Time

A full-time CFO in the UK typically costs:

• Base salary: £150,000-£250,000+
• Employer's National Insurance: £20,000-£35,000
• Pension contributions: £5,000-£12,000
• Benefits: £5,000-£15,000
• Equity: typically 0.5-2% (immediate dilution)
• Recruitment fees: £35,000-£75,000 one-off, often 25-30% of base salary

Total Year 1: roughly £210,000-£360,000+ plus equity dilution.

A fractional CFO at around one day per week costs £48,000-£96,000 a year — typically 60-80% less than the all-in cost of a full-time hire, with no equity dilution, no recruitment fees, and no severance exposure if your needs change.

Fractional CFO vs Full-Time CFO

Choose fractional when: the finance workload is strategic but not yet a five-day-a-week job, you raise every 12-24 months rather than run continuous corporate-finance activity, or your runway means every senior hire has to justify itself.

Choose full-time when: you have a finance team that needs daily executive leadership, you are running M&A, international expansion or complex revenue operations, or post-Series B governance genuinely demands a full-time seat at the table.

The honest answer for most pre-seed to Series A startups is that the full-time question simply arrives later. A good fractional CFO will tell you when you have outgrown them — and help you hire their replacement.

Fractional CFO vs Accountant vs Financial Controller

These three roles are often confused, and the confusion is expensive in both directions — founders either pay CFO rates for bookkeeping, or expect strategic finance from an accountant who was never hired to provide it. The distinction is about time horizon:

Accountant — Historical & Compliance

• Answers: what happened, and are we compliant?
• Covers: statutory accounts, corporation tax, VAT returns, payroll, Companies House filings
• Cadence: monthly to annually, deadline-driven
• Typical cost: a few hundred pounds a month outsourced at early stage

Financial Controller — Operational

• Answers: are the numbers right, and is the machine running?
• Covers: bookkeeping oversight, month-end close, invoicing and collections, spend controls, management accounts production
• Cadence: daily to monthly
• Typically arrives: once transaction volume outgrows the founder-plus-accountant setup

Fractional CFO — Strategic & Forward-Looking

• Answers: where are we going, and can we afford to get there?
• Covers: financial modelling, runway scenarios, fundraising and data rooms, pricing and unit economics, board narrative
• Cadence: weekly rhythm, quarterly deep work, intense around a raise
• Typically arrives: pre-seed to Series A, usually triggered by a raise or a round just closed

How to Choose a Fractional CFO

Green Flags

• Sector experience — They know your business model's economics, whether that is fintech, healthtech or B2B SaaS
• Stage fit — Pre-seed to Series A finance is a different craft from corporate finance; scrappy data and fast decisions should not faze them
• Fundraising track record — They have supported rounds like the one you are planning and know what UK investors actually ask
• Hands-on with models — They build and maintain the model themselves, rather than reviewing someone else's work from a distance
• Plain-English communication — They make the numbers clearer, not more intimidating; you will spend hours together, so chemistry matters

Red Flags

• Compliance background rebadged — A career in historical reporting does not automatically translate into forward-looking strategy
• Template models — If every model they show ends in the same hockey stick, the assumptions are decoration, not analysis
• Overcommitted — Too many concurrent clients means your board week gets whatever attention is left over
• Can't face investors — If they cannot defend the model in a diligence conversation, you will be doing it alone
• Equity-first pricing — Fractional engagements should be cash-based; significant equity is for full-time commitment

Questions to Ask

1. "Which fundraises have you supported at our stage, and what was your role in them?"
2. "Walk me through a model you built. Which three assumptions mattered most, and how did you test them?"
3. "How would you approach our cash position and runway in your first 30 days?"
4. "What does a monthly reporting rhythm look like with you — what do we get, and when?"
5. "What would make you advise us not to raise?"

That last question matters. A fractional CFO's job is to tell you the truth about your numbers, including when the truth is inconvenient. Anyone who treats every situation as raise-ready is selling, not advising.

Working with a Fractional CFO

A well-run fractional CFO engagement has a predictable shape. Here is what to expect — and what to insist on.

The First 30 Days: Diagnostic

The engagement should open with a clear-eyed review of where you stand:

• Cash position and a first-cut 13-week cash flow
• Review (or rebuild) of the financial model and its assumptions
• A baseline for reporting: what the board and investors currently see, and what they should
• Quick wins — cost anomalies, billing gaps, working-capital timing

The Ongoing Cadence

• Weekly: a founder sync, plus async availability for decisions that cannot wait
• Monthly: management accounts, KPI pack and budget-versus-actuals review
• Quarterly: reforecast and a strategic review of runway, hiring and pricing
• Around a raise: intensity increases — model, data room, investor Q&A support

The Deliverables You Should Expect

• A three-statement financial model you own and understand
• A 13-week cash flow, maintained, with runway scenarios
• A monthly board and investor pack produced on time
• An investor-ready data room, kept current between rounds
• Documented unit economics and pricing analysis

Related reading: Building your first data room →

Tools and Ownership

Expect the work to live in tools you control: your accounting platform (typically Xero or QuickBooks), spreadsheet models shared in your own drive, and dashboards built on your data. Everything should be documented and owned by the company — if the engagement ends, the model, the data room and the reporting rhythm stay with you. A fractional CFO who keeps the model as a black box has built a dependency, not a finance function.

Frequently Asked Questions