Ask any operator who's been through a near-miss what they wish they'd had earlier, and the answer is almost always the same: a rolling 13-week cash flow forecast. Annual budgets are fiction by month three. Monthly P&Ls arrive after the damage is done. The 13-week is the only tool we've seen consistently surface problems early enough to fix them.
This is the template we install in every engagement.
Why 13 weeks specifically
Thirteen weeks is one quarter, one rolling, weekly. The structure does three things:
- It's long enough to see the gap between sales and collections clearly
- It's short enough that every line is defensible — no fairy dust assumptions five quarters out
- It's weekly, so trends show up before they become months
Most founders try to skip to a longer horizon. Don't. The horizon is wrong; the granularity is what catches problems.
The structure (one tab, three sections)
Section 1 — Opening cash
Start with the actual bank balance Monday morning. Not the closing balance from your last close. The actual number, today.
Section 2 — Inflows by week
For each of the next 13 weeks, model:
- Existing AR collections — by customer, by expected pay date; aged appropriately
- New revenue — separated by committed (contract signed) and forecast (in pipeline)
- Non-revenue cash — financing, tax refunds, anything else
The discipline that matters: committed and forecast on separate lines. Most cash crises come from treating forecast as committed.
Section 3 — Outflows by week
For each of the next 13 weeks:
- Payroll — by pay date, including taxes and benefits
- Recurring vendor payments — SaaS, rent, insurance, agency retainers
- One-time payments — equipment, legal, professional fees, taxes
- Debt service — interest and principal, by due date
If you have variable costs tied to revenue (COGS, commissions), model those as a percentage that flows from Section 2.
The single number that matters
At the bottom of the model: closing cash by week, with conditional formatting that turns red if any week dips below your minimum threshold.
Pick the threshold honestly. We usually recommend 8 weeks of payroll as the floor. Anything below that is operating in the danger zone, regardless of revenue.
The weekly cadence that makes it work
The forecast is worthless if it's a quarterly exercise. The cadence:
- Every Monday, 30 minutes — finance or fractional CFO updates the forecast with last week's actuals and any new commitments
- Variances over 5% are flagged in writing — not just on the chart
- The forecast goes to the CEO every Monday by 9am
If you don't have anyone to run this, this is the first thing a fractional CFO does on day one. It's also the cheapest engagement we ever run, and the one with the most lopsided return on investment.
What the forecast catches that the P&L misses
- The collection cliff — three big invoices land in week 8, but if they slip to week 11, you can't make payroll in week 9
- The vendor stack-up — annual renewals quietly clustering in the same week
- The growth squeeze — a new contract that should be great cash flow but actually consumes cash before it produces it
The P&L will smooth all three of these into the wrong number. The 13-week shows them as walls.
The mistake to avoid
The mistake is treating the forecast as a planning tool. It is not. It is an early warning tool. Don't optimize it. Don't make it pretty. Don't add 40 lines.
A forecast that gets updated every Monday will save your company someday. A forecast that lives in a beautiful dashboard nobody touches will not.
Related reading:
- The four numbers a founder should know cold every Monday
- The KPIs that actually predict business health — and the ones that fool everyone
- Fractional COO or full-time COO? A decision framework with real cost math
The 13-week forecast is the first artifact we install in every Business Operations Consulting engagement.
