You closed your Series A with a plan to scale revenue, hire ahead of the curve, and give your board better visibility than a monthly spreadsheet. What you may not have budgeted for is the finance function that makes all of that possible: a close process that holds up under diligence, a forecast your leadership team actually uses, and someone in the room who can translate burn, runway, and unit economics without hedging. A fractional CFO is often the fastest way to get that capability without committing to a six-figure full-time hire before your revenue base justifies it.
What a fractional CFO owns at Series A
At this stage, the job is less about corporate development and more about building the operating system your company runs on. A strong fractional CFO sets the monthly close calendar, defines chart-of-accounts standards, and makes sure your revenue recognition matches how you sell, not how your bookkeeper inherited the setup from seed stage. They own the board deck narrative: cash position, hiring plan versus plan, gross margin trends, and the assumptions behind your forecast.
They also sit at the intersection of finance and everything else. That means partnering with your head of sales on pipeline-to-cash timing, working with HR on headcount planning and option pool modeling, and flagging when a new vendor contract creates a balance-sheet obligation your CEO has not thought about. The best fractional CFOs do not wait to be asked. They show up with a 90-day priorities list on day one and adjust it after the first board meeting.
When you need one, and when you can wait
You likely need fractional CFO support if you have raised institutional capital and your investors expect monthly reporting, if you are hiring finance-adjacent roles without a senior finance leader to direct them, or if you are preparing for a Series B process in the next 12 months and your historical financials will not survive a data room review. Another clear signal: your CEO or COO is still the person reconciling the bank account or building the forecast in Excel at midnight.
You can often wait if you are pre-revenue with a simple cap table, if your bookkeeper and a part-time controller already produce clean monthly financials on a five-day close, or if your burn is low enough that runway math is a 10-minute exercise. Fractional CFOs are a poor fit when what you actually need is transactional bookkeeping. That is a different hire at a different price point. Be honest about which problem you are solving.
What the first 90 days should look like
Week one is diagnostic: systems access, a review of the last three months of financials, and interviews with whoever touches money today. By day 30, you should have a documented close process, a corrected baseline forecast, and a short list of accounting gaps ranked by investor and audit risk. Days 31 through 60 focus on execution: first board-ready package, vendor and contract review, and alignment with your tax advisor on entity structure and estimated payments.
Days 61 through 90 shift toward forward planning: scenario models for hiring plans, a dashboard your leadership team reviews weekly, and clear ownership for every recurring finance workflow. If your fractional CFO cannot articulate what "done" looks like at each of these milestones, that is a red flag. The engagement should feel like a project with a operating rhythm, not an open-ended retainer with vague "strategic support."
Choosing a provider comes down to relevant stage experience, references from founders (not just other advisors), and whether they will embed in your tools and meetings or stay arms-length. Ask for a sample board deck they have produced, how they handle month-end when your team is unavailable, and what happens when you outgrow fractional scope. The right partner makes your next fundraise easier; the wrong one leaves you rebuilding the same infrastructure twice.
The related operating work is Outsourced CFO.