Part-Time CFO vs Full-Time CFO: Which Does Your SaaS Need?
Part-time vs full-time CFO for SaaS companies. Cost comparison, when each makes sense, and how to transition from one to the other as you grow.
The question is not whether your SaaS company needs CFO-level finance support. It does. The question is whether you need someone five days a week or two to four days a month.
Most SaaS companies between £500K and £10M ARR do not need a full-time CFO. They need the output of a CFO -- a financial model, monthly management accounts, variance analysis, cash flow forecasting, board reporting -- without the £150K+ salary, the employer’s NI, the pension contributions, and the six-month recruitment process.
That is what a part-time CFO provides. This guide breaks down the cost comparison, when each option makes sense, and how to transition from part-time to full-time when your company outgrows the model.
The cost comparison
The numbers are straightforward. Here is what each option costs a UK SaaS company:
Full-time CFO
| Cost item | Annual cost |
|---|---|
| Base salary | £150,000 - £250,000 |
| Employer’s NI (15%) | £21,750 - £36,750 |
| Pension (5%) | £7,500 - £12,500 |
| Private medical & benefits | £2,000 - £5,000 |
| Recruitment fee (20%, amortised) | £30,000 - £50,000 |
| Total year 1 | £211,250 - £354,250 |
After year 1, remove the recruitment fee. The ongoing cost is £181,250 to £304,250 per year.
Part-time CFO
| Cost item | Annual cost |
|---|---|
| Monthly retainer (2-4 days/month) | £24,000 - £60,000 |
| No NI, pension, or benefits | £0 |
| No recruitment fee | £0 |
| Total | £24,000 - £60,000 |
A part-time CFO costs 11-28% of a full-time hire in year 1 and 13-33% on an ongoing basis. For a company burning £100K-£200K per month, that difference is meaningful -- it is the equivalent of one to two additional engineers or three to four months of extended runway.
When a part-time CFO is the right choice
A part-time CFO works well when your finance needs are strategic but not continuous. That typically means:
Pre-Series A (under £3M ARR). You need a financial model, monthly reporting, and investor-ready materials. You do not need someone sitting in the office five days a week to produce them. Two to three days per month covers the model build, monthly management accounts, and ad hoc support for fundraising conversations.
Post-seed, pre-Series B (£3M-£10M ARR). The work increases. You need board packs, detailed variance analysis, cash flow forecasting, and support for the finance team (typically a bookkeeper or financial controller). Three to four days per month handles this, with additional days during fundraising periods.
No internal finance team. If your only finance person is a bookkeeper or an outsourced accountant, a part-time CFO provides the strategic layer on top. They review the bookkeeper’s work, produce management accounts, build the financial model, and present to the board.
Fundraising preparation. A part-time CFO can build your data room, clean up your financials, prepare your model, and coach you through investor due diligence -- all on a retainer rather than a permanent hire.
When a full-time CFO makes sense
There is a point where part-time support is no longer sufficient. That point typically arrives when:
You are post-Series B with £15M+ ARR. At this scale, you have a growing finance team (controller, FP&A analyst, accounts payable/receivable). Someone needs to manage that team day-to-day, not just two days a month.
You are preparing for an IPO or a large exit. The regulatory, compliance, and reporting requirements for a public listing or a trade sale above £50M require a full-time CFO who is deeply embedded in the business. Companies House filing obligations increase, audit requirements become more demanding under FRS 102 (or IFRS if you are listing), and the due diligence process alone can consume 20-30 hours per week for months.
You have complex international operations. Multiple entities, transfer pricing, multi-currency treasury management, and cross-border tax planning require continuous attention that a part-time engagement cannot provide.
You need a CFO on the leadership team. If your investors or board expect the CFO to attend every leadership meeting, contribute to product and go-to-market strategy, and be available for ad hoc decisions daily, that is a full-time role.
What a part-time CFO delivers in 2-4 days per month
The output of a good part-time CFO is the same as a full-time one. The difference is the time allocation, not the quality. In a typical month:
Day 1: Management accounts and variance analysis. Review the bookkeeper’s work, post accruals and prepayments, reconcile revenue to the MRR schedule, and produce a P&L with commentary. Compare actuals against budget and explain material variances.
Day 2: Financial model and forecasting. Update the 3-way financial model (P&L, balance sheet, cash flow) with the latest actuals. Extend the forecast. Run scenarios if needed -- what happens if churn increases by 50%? What if we delay that hire by three months?
Day 3: Board pack and strategic work. Prepare the monthly or quarterly board pack with financial performance, KPIs, and commentary. Handle ad hoc requests: pricing analysis, unit economics review, vendor negotiation support.
Day 4 (if included): Fundraising and investor relations. Update the data room, prepare investor materials, model scenarios for different funding amounts, and support due diligence questions.
Between the scheduled days, a part-time CFO is typically available by email and Slack for quick questions. You are not paying for idle time -- you are paying for focused, high-value output.
How the engagement works
A typical part-time CFO engagement has four components:
Monthly retainer. Fixed fee for an agreed number of days per month. Most engagements are 2-4 days, with the option to flex up during busy periods (fundraising, year-end, audit). Expect to pay £2,000-£5,000 per month depending on the scope and the CFO’s experience.
Scope definition. At the start of the engagement, you agree on what is included: management accounts, board packs, financial model, cash flow forecast, variance analysis, and any project work (fundraising support, R&D tax credit claims, budget build). This prevents scope creep and ensures both sides know what is expected.
Communication rhythm. Most part-time CFOs work with a monthly cadence: receive the data in week 1, produce the accounts and analysis in week 2, present to the founder or board in week 3, handle follow-ups in week 4. Between monthly cycles, communication is asynchronous -- Slack messages, short calls, email.
Notice period. Part-time CFO engagements typically have a one to three month notice period on either side. Compare that to a full-time hire, where you might face a six-month notice period plus the risk of a costly unfair dismissal claim if things do not work out.
Transition plan: from part-time to full-time
The best part-time CFO engagements include a natural transition path. Here is how it works:
Phase 1 (months 1-6): Foundation. The part-time CFO builds the financial model, establishes the reporting cadence, cleans up the chart of accounts, and produces the first proper management accounts. This is the phase where most of the heavy lifting happens.
Phase 2 (months 7-18): Optimisation. The model is built. The reporting cadence is established. The part-time CFO focuses on variance analysis, forecasting accuracy, and strategic projects. This is also when you should be hiring a financial controller or FP&A analyst -- someone who handles the day-to-day bookkeeping and data preparation, freeing the part-time CFO for higher-value work.
Phase 3 (month 18+): Handover or scale. At this point, one of two things happens. Either the company’s needs have grown beyond what a part-time CFO can deliver (typically at £10M+ ARR), and you hire a full-time CFO with the part-time CFO supporting the transition. Or the model continues to work well, and the engagement continues.
The advantage of this approach is that when you do hire a full-time CFO, they inherit a clean set of accounts, an established reporting cadence, a working financial model, and a board that is used to receiving quality financial information. They hit the ground running instead of spending their first six months building what should already exist.
How to choose the right part-time CFO
Not all part-time CFOs are created equal. For a SaaS company, look for:
- SaaS experience. They must understand MRR, ARR, churn, LTV, CAC, and the unit economics that drive SaaS valuations. A CFO from manufacturing or retail will not know how to build an MRR waterfall.
- Accounting qualification. A recognised UK accounting qualification (CIMA, ACCA or equivalent). This matters because they will be reviewing your accounts, signing off on management accounts, and potentially supporting your audit. An unqualified "CFO" is a financial controller at best.
- Fundraising experience. If you plan to raise capital, your part-time CFO should have experience building investor models, managing data rooms, and supporting due diligence.
- UK tax knowledge. R&D tax credits, EMI share options, corporation tax planning, VAT schemes -- these are UK-specific and materially affect your cash position. HMRC does not accept "my CFO was not aware" as an excuse.
- References from other SaaS founders. Ask for them. Call them.
The bottom line
For most SaaS companies between £500K and £10M ARR, a part-time CFO at £2K-£5K per month delivers the same strategic output as a full-time hire at £150K-£250K per year. The cost saving is substantial, the flexibility is higher, and the risk is lower.
When you outgrow the model -- and you will, if things go well -- you transition to a full-time hire with a clean foundation already in place. That is the smart path.
If you want to explore whether a part-time CFO is right for your company, get in touch for a conversation about your needs.