What a fractional CFO does for a startup
A startup does not need a CFO to record transactions. It needs one to answer the questions that decide whether the company survives the next 18 months: how much runway is left, how much to raise and when, what the next hire does to burn, and whether the numbers in the deck will hold up in diligence. A fractional CFO answers those questions for a few hours a week and leaves the daily bookkeeping to the people already doing it.
The work usually covers six areas:
- Runway and burn model. A driver-based model tied to headcount, revenue and spend, so you can see the cash-out date move when you change one assumption in a meeting.
- Fundraising preparation. The financial model investors will open, the use-of-funds slide, round sizing, and cap table scenarios for SAFEs, convertible notes and a priced round.
- Investor data room. Clean financial statements, revenue by customer, cohort and retention data, contracts and the cap table, organized before the first partner meeting instead of after the term sheet.
- Board and investor reporting. A monthly or quarterly package with burn, runway, revenue and the few metrics your investors actually track.
- Unit economics. Customer acquisition cost, payback, gross margin and net revenue retention, calculated the way investors calculate them.
- Compliance basics. Coordination of the 409A valuation, sales tax exposure in states where you have customers, revenue recognition for annual contracts, and the handoff to your tax preparer.
What the CFO does not do is daily data entry or the tax return itself. Your bookkeeper or accounting service still closes the books, and a CPA still files. The CFO turns those books into decisions and into a story investors trust.
When should a startup hire a fractional CFO
Most founders feel the gap at one of three moments. The first is three to six months before a priced round, when the spreadsheet that got you through pre-seed will not survive a VC analyst. The second is right after a round closes, when there is a board to report to and real money to deploy. The third is when burn climbs past roughly $100,000 a month and nobody can say with confidence what runway looks like.
Other clear signals:
- An investor asked for a model, a cohort table or a net revenue retention number and it took you a week to produce.
- The founder who knows the numbers is also running product or sales, and the finance work happens at midnight.
- Your books close 30 or more days late, so every board update uses numbers that are already stale.
- You are about to sign a large customer contract, a lease, or a debt facility and want someone senior to check the terms.
- You have customers in many states and nobody has checked where you owe sales tax.
If the books themselves are messy, start with cleanup. A fractional controller gets the records current and the CFO starts once there is something reliable to model from.
How many hours a week a startup CFO needs
These scopes are typical on Side.work for a startup that already has a bookkeeper or an outsourced accounting service.
| Stage | Hours a week | What you get |
|---|---|---|
| Pre-seed and seed | 3 to 5 | Runway model, monthly burn review, investor update numbers, 409A and cap table coordination |
| Raising a Series A | 10 to 15 for 2 to 4 months | Investor-grade model, data room, diligence answers, round sizing and term sheet review |
| Post Series A | 8 to 12 | Budget and forecast, board package, hiring plan vs burn, unit economics, finance team build-out |
| Series B prep | 15 to 20 | Audit readiness, revenue recognition review, planning system, preparing to hand off to a full-time CFO |
Fundraising is the uneven part. The weekly cap on a Side.work contract can go up for the raise and come back down once the money is in the bank, without renegotiating the whole engagement.
How much does a fractional CFO cost for a startup
Senior fractional CFOs on Side.work set their own rates, usually $175 to $300 an hour, and CFOs who have closed several venture rounds sit at the top of that range. Monthly cost is the hourly rate times hours per week times 4.33. At 5 hours a week that is roughly $3,800 to $6,500 a month. At 10 hours it is roughly $7,600 to $13,000 a month in specialist fees. Some CFOs also offer a fixed fee for a fundraising project; you see each rate on the shortlist before you send an intro.
On top of the hours you pay the platform fee for your plan, 12 percent on Starter, 8 percent on Growth and 5 percent on Scale, plus the plan subscription. A seed-stage company hiring one CFO usually fits the Starter plan at $99 a month. The full breakdown is on the pricing page, and our guide to fractional CFO hourly rates and monthly cost shows the cost at every common hour level.
Compare that with a full-time startup CFO. Base salary alone for an experienced venture-backed CFO is well into six figures before equity and benefits, and most seed and Series A companies do not have 40 hours a week of CFO work. Paying for 8 hours of senior judgment and keeping the rest of the budget for engineers and sales is the reason fractional is the default at this stage.
A typical week, Fractional CFO
10 hours a week
- Hourly rate
- $175 to $300
- Monthly cost
- $7,600 to $13,000
Startup fractional CFO vs outsourced accounting vs full-time CFO
Founders often ask why they need a CFO when an accounting service already sends them financial statements. Each option answers a different question.
| Option | Main question it answers | Typical output | Best fit |
|---|---|---|---|
| Outsourced bookkeeping or accounting service | What happened last month? | Closed books, reconciliations, financial statements | Every startup from day one |
| Fractional CFO on Side.work | How long is our runway and how do we raise? | Runway model, fundraising materials, board package, unit economics | Seed to Series B, 3 to 20 hours a week |
| Full-time CFO | How do we run finance as a department? | Finance team, audit, planning system, investor relations | Later stage, usually after a large round or ahead of an exit |
Several outsourced accounting services also sell a CFO tier. That can work well, but the CFO is assigned by the firm. On Side.work you see the person, their stage experience and their weekly availability before you choose, and you can keep your current bookkeeping provider.
What the first 90 days look like
In the first month the CFO gets read access to the accounting system, the bank, payroll, billing and the cap table, then rebuilds burn and runway from actuals. Founders often learn something here, usually that runway is two or three months shorter than they thought once annual prepaid contracts and upcoming hires are counted correctly.
In the second month they build the operating model and agree a monthly reporting routine: what goes to the board, what goes in the investor update, and which five metrics everyone tracks. In the third month the model starts earning its keep. Scenarios for the hiring plan, a fundraising timeline working back from the cash-out date, and a data room skeleton so the next raise starts organized.
By day 90 a founder should be able to answer three questions in one sentence each: when do we run out of cash, how much should we raise, and which metric has to improve before we do.
How hiring a startup CFO works on Side.work
Pick fractional CFO, enter the hours per week and your budget, and add a line about the company, for example a seed-stage B2B SaaS company with $1.2 million ARR planning a Series A next year. Side.work returns a ranked shortlist of verified CFOs with live weekly availability and their hourly rate, so you only talk to people who can fit your schedule and budget.
Every profile is checked for a work email domain, a LinkedIn profile, live portfolio links and payout identity, and each specialist confirms their side work does not conflict with their employment terms. Send intros, take a call, then sign a contract with a weekly hours cap and a notice period. An NDA is attached by default, which matters when the CFO sees your cap table and investor terms. Each week the CFO submits a timesheet, you approve the hours and pay one invoice. The full flow is on how it works.
Running a profitable, owner-led business rather than a venture-backed startup? The page on a fractional CFO for small business covers lenders, margins and owner reporting instead. If you are also missing technical leadership, the same shortlist works for a fractional CTO.
Questions to ask a startup CFO before you hire
- Which rounds have you helped raise, at what stage, and what did investors push back on in diligence?
- Show us a runway model you built, with the names removed. Which drivers does it hang on?
- How do you calculate net revenue retention and CAC payback for a company like ours?
- How have you handled a SAFE or convertible note conversion in a priced round?
- What would you change in our monthly investor update?
- How many clients do you carry, and how do you handle the weeks of an active raise?
Strong candidates answer with specifics: the round, the investor, the model, what changed after they arrived. Talk to two or three before you decide. Your plan includes the intros to do it.