The SaaS CFO Service for UK Founders
Sourced benchmarks your board can trust, board packs that reconcile end to end, and a fixed retainer of £2,000-£5,000 a month. No day rates, no equity, no surprises.
- Price £2K-£5K per month fixed retainer. No day rates, no equity, no recruitment fees.
- Scope MRR schedule reconciled to the accounts, monthly board pack with sourced benchmark comparison, 12-month cash flow forecast, fundraising and exit support. Same full-service scope at every tier.
- Terms Month-to-month with 30-day notice. Fully remote across the UK. The CFO you speak to is the CFO who does the work.
- Best for UK SaaS and AI founders at £250K to £5M ARR raising SEIS, EIS, Seed or Series A.
Do you recognise this?
Most SaaS founders between £500K and £5M ARR do not have anyone looking at their numbers with a critical eye. If two or more of the following apply, your data is not investor-ready.
UK SaaS benchmarks your board will ask about
Most benchmark numbers quoted at UK boards come from public-company data or from nowhere at all. The figures below are private B2B SaaS medians from the two largest annual surveys: Benchmarkit's 2025 report (583 companies, CY-2024 data) and SaaS Capital's 14th annual survey (1,000+ companies). Quick glossary: NRR is revenue retained and expanded from existing customers over 12 months; GRR is revenue retained before any expansion; CAC payback is the months of gross profit needed to recover the cost of acquiring a customer; burn multiple is net burn divided by net new ARR.
| Metric | Median (CY-2024) | Best in class | Source |
|---|---|---|---|
| ARR growth (private B2B SaaS) | 25% overall; 28% at $1-3M ARR, 24% at $5-10M | Top quartile: 50% at $1-3M ARR, 42% at $5-10M | SaaS Capital, 2025 |
| Net revenue retention (NRR) | 101% | 110% (top quartile) | Benchmarkit, 2025 |
| Gross revenue retention (GRR) | 88% | 95% (top quartile) | Benchmarkit, 2025 |
| Customer (logo) churn | n/a in this survey | Under 2% per month | ChartMogul, 2023 |
| Gross margin (blended) | 77% (81% subscription-only) | 84% (top quartile) | Benchmarkit, 2025 |
| CAC payback period | 18 months | 12 months (most efficient quartile) | Benchmarkit, 2025 |
| New customer CAC ratio | $2.00 to acquire $1 of new ARR | $1.00 for expansion ARR | Benchmarkit, 2025 |
| Rule of 40 score | 15% | 35% (top quartile) | Benchmarkit, 2025 |
| Burn multiple | 1.2x at $1-5M ARR; 1.5x at $5-20M | 1.0x at $20-50M ARR; 0.9x at $50-100M (medians) | Benchmarkit, 2025 |
| Sales & marketing spend | 37% of revenue | Bootstrapped median 28%; VC-backed 45% | Benchmarkit, 2025 |
All figures are private-company data from USD-denominated surveys; UK companies are benchmarked against the same global private datasets. The ChartMogul churn figure covers the 12 months to March 2023. Two independent surveys put 2024 median growth within one point of each other - 26% at Benchmarkit, 25% at SaaS Capital - which is why board packs should anchor to them rather than to public-company comparables.
Retention is the strongest growth predictor in the data. Companies above 130% NRR grew at a 44% median in 2024 against 15% for those below 90%, and the highest-NRR cohort grows 83% faster than the population median (SaaS Capital, 2025). SaaS Capital's separate retention study corroborates the Benchmarkit medians: 102% median NRR in the $25K-$50K ACV cohort (SaaS Capital retention benchmarks, 2025). One rare verified regional cut: the median Rule of 40 score is 9% for US companies against 25% for EMEA (Benchmarkit, 2025) - European SaaS runs leaner than the US narrative suggests.
For the full stage-by-stage breakdown, see our B2B SaaS metrics benchmarks guide.
ScaleWithCFO engagement benchmarks
The table above is survey data. The table below is different: it is what we look for inside client models across 47 SaaS and AI engagements - the shape of the numbers, not the survey median. These are ScaleWithCFO practice benchmarks, clearly labelled as such, not an external study.
| What investors read | What good looks like |
|---|---|
| Growth (VC-funded) | Roughly 3x, 3x, then 2x year on year - £1M ARR to £2M+ within 12 months |
| Growth (bootstrapped / angel) | At least 60% a year, with months close to profitability |
| Revenue shape | Steady, never lumpy, with recurring revenue rising as a share of total |
| Sales & marketing | 20-30% of revenue, growing in line with the growth you claim |
| Customer support | 10% of revenue at most - a product that needs more support does not scale |
| Gross margin | Climbing steadily to 70-80% - anything near 90% means costs are hiding |
| R&D and product | The biggest share of spend - this is what builds long-term value |
| Efficiency | CAC falls as you scale, and revenue per employee rises |
Two worked examples
Rule of 40: 25% growth, 10% EBITDA
The Rule of 40 adds revenue growth to profit margin, with 40 as the bar. A company growing 25% with a 10% EBITDA margin scores 35 - comfortably above the 15% private-company median, yet still below the number investors price against. The CFO levers are specific: reclassify cost of sales so gross margin is real, cut the sales spend that is not converting, and reprice the weakest cohort. Growth at 28% and margin at 13% clears the bar without a new product line.
CAC payback: £120K spend, 20 customers
Spend £120,000 on sales and marketing in a quarter and sign 20 customers at £6,000 annual contract value each: CAC is £6,000 per customer. At an 80% gross margin, each customer returns £400 of gross profit a month, so payback is 15 months - inside the 18-month median but short of the 12-month top quartile. The full method, including channel-level cuts, is in our SaaS unit economics guide.
Investors read the shape of the model before they read the cells. Every ScaleWithCFO board pack shows your NRR, CAC payback and Rule of 40 against the sourced medians above, so the board debates performance rather than the data. Book a free 15-minute call.
What the SaaS CFO engagement covers
Your accountant looks backwards at what happened; a SaaS CFO looks forward at what should happen next. The engagement is hands-on execution, not advisory-only - the same scope a full-time hire would cover, delivered as a fractional CFO service.
- Month-end close and clean-up. Revenue recognition under FRS 102 / IFRS 15, chart of accounts rebuilt by department, Xero reconciled to Stripe and your CRM, COGS allocation corrected so gross margin reflects commercial reality.
- MRR schedule and metrics layer. Customer-level MRR movements (new, expansion, contraction, churn), NRR and GRR, cohort analysis - every metric traceable to the ledger.
- Cash flow forecasting. A 12-month operational forecast with base, upside and downside runway scenarios, so you know when the cash runs out under each. Method in our cash flow forecasting guide.
- Monthly board pack. MRR waterfall, ARR bridge, CAC by channel, benchmark comparison and commentary. See the monthly reporting service and the investor-grade board pack structure.
- Fundraising and financial models. Data room prep, due diligence support and the model itself - see the guides on building a seed financial model and the Series A model. £21.3M raised for clients to date.
- Unit economics and exit preparation. CAC payback and LTV by channel, customer concentration analysis, and valuation positioning against the current UK SaaS multiples.
Pricing - £2,000-£5,000/month full-service nationwide
Every engagement covers the same full-service scope. The retainer scales with business complexity - more entities, more contracts, more reporting cadence - not feature access. A Pre-Seed founder paying £2,000 a month gets the same scope of work as a Series A+ company paying £5,000.
Cash flow survival, first financial model, first board pack, SEIS / EIS compliance. One monthly review plus ad-hoc support between calls.
Fundraising model, investor reporting, monthly management accounts under FRS 102, unit economics tracking. Bi-weekly cadence.
Finance team oversight, complex modelling, M&A support, multi-entity structure. Weekly cadence when needed, plus board meeting attendance.
The band is confirmed in writing after the discovery call, NDA and a look at your financials, so the retainer reflects the actual scope of work. Compared to a full-time CFO at £150K-£250K base plus 1-5% equity, the fractional model delivers the same scope at roughly 10-20% of the all-in cost.
See how much a fractional CFO costs in the UK for the full pricing breakdown and what is included in every engagement.
What founders say
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"Constantin knows his stuff and it was a really professional experience working with him. We will keep engaging Constantin to support us with our financial strategy. Only positive things to say about his services."
"Our CFO Constantin is always there for us, with clear reporting, useful insights (that we can't see as we are too close), and quick replies to our questions. A fractional CFO makes so much sense. A lifetime of experience at a fraction of the cost."
The CFO behind ScaleWithCFO
ScaleWithCFO is run by Constantin Botnari, a CIMA qualified accountant working directly with SaaS, AI and technology founders across London and the UK. Founder-led and direct - the CFO you speak to is the CFO who does the work.
Whether the job is preparing to raise, cleaning up historical data or planning an exit, the work is done hands-on so founders can focus on building the business.
From first call to fully operational in 90 days
Every engagement follows the same proven structure. By day 90, your financials are clean, your forecast is built, and your first board pack is delivered.
Clean up & restructure your financials
- Rebuild your chart of accounts by department (Sales, Marketing, Development, G&A)
- Fix how revenue is recorded - spread annual contracts across 12 months under FRS 102
- Split costs correctly between cost of sales and operating expenses
- Reconcile Xero with subscription data from Stripe, HubSpot and your CRM
- Audit gross profit margin and correct COGS allocation
- Review historical data so investors see a clean, consistent trail
Cash flow forecast & financial planning
- Build an operational cash flow forecast with scenario analysis
- Calculate runway under conservative, base and best-case scenarios
- Review your sales pipeline and model expected revenue by cohort
- Set budgets with team leaders for the next 12 months
- Build unit economics - acquisition cost, lifetime value, payback period
- Identify cash leaks and opportunities to extend runway
First board pack delivered
- Monthly report with KPIs, management commentary and recommendations
- Revenue waterfall: new customers, expansions, downgrades, churn, net new
- Retention metrics benchmarked against the sourced medians on this page
- Efficiency metrics: CAC payback, burn vs growth, LTV/CAC ratio
- Customer concentration and cohort analysis
- Strategic planning aligned to your fundraising or exit timeline
Frequently asked questions
A SaaS CFO works natively in subscription mechanics: MRR and ARR bridges, deferred revenue under FRS 102, net revenue retention, cohort analysis, CAC payback and burn multiple. A generalist CFO can learn these but spends the first months of the engagement on the learning curve while you pay for the time. A specialist also brings benchmark context - knowing, for example, that the private B2B SaaS median NRR is 101% (Benchmarkit, 2025), not the 110-120% often quoted from public-company data.
The CFO should own the metrics investors test first: MRR and ARR movements, net revenue retention (private-company median 101%), gross revenue retention (median 88%), gross margin (median 77% blended, 81% subscription-only), CAC payback (median 18 months), burn multiple and the Rule of 40 (median score 15%). Every one of them must reconcile back to the accounting data - a metric that cannot be traced to the ledger fails due diligence. Benchmarks from Benchmarkit's 2025 survey of 583 private B2B SaaS companies.
ScaleWithCFO charges a fixed monthly retainer of £2,000-£5,000 banded by stage: Pre-Seed / Seed £2,000-£3,000, Seed / Pre-Series A £2,500-£4,000, Series A+ £3,500-£5,000. Every tier gets the same full-service scope - the retainer scales with business complexity, not feature access. Terms are month-to-month with 30-day notice, no day rates, no equity, no recruitment fees. A full-time SaaS CFO costs £150K-£250K base plus 1-5% equity.
Typically between £500K and £5M ARR, once there is product-market fit and a fundraise or exit on the horizon. The practical trigger: an investor asks for net revenue retention, CAC payback or cohort data and the answer cannot be produced from the accounts. Fixing revenue recognition and historical data takes two to three months, so the right time to start is before the raise, not during it.
Yes. AI companies run the same subscription or usage-based model with added cost complexity: compute and inference costs belong in cost of sales, which pressures gross margin against the 77% B2B SaaS median (Benchmarkit, 2025), and model training spend affects R&D tax relief claims. The reporting framework - MRR, NRR, CAC payback, burn multiple - is identical.
A board pack should show each core metric against a sourced external benchmark: net revenue retention against the 101% private-company median and 110% top quartile, gross revenue retention against 88%, CAC payback against 18 months, Rule of 40 against the 15% median, and burn multiple against the 1.2x median for $1-5M ARR companies. Sources worth anchoring to are Benchmarkit's 2025 benchmarks (583 companies) and SaaS Capital's 14th annual survey (1,000+ companies). Unsourced benchmarks invite the board to argue with the number instead of the performance.
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