VickeryFinance • Small Business Finance

How to Make a Cash Flow Forecast Your Future Self Trusts

Profit is an opinion about a month; cash is a fact about a Friday. A rolling 13-week forecast shows the exact week money gets tight — while there is still time to do something about it.

13 weeksone quarter — far enough to act, close enough to be right

$8,750the low point in the worked example

Weeklyupdate it the same day you reconcile

Why thirteen weeks

A month is too short: the payroll, rent, and quarterly tax payment that hurt you are always visible but never avoidable in four weeks. A year is too long: inflow guesses that far out are fiction wearing a spreadsheet. Thirteen weeks — one quarter — is the working horizon where receivables, payables, and the calendar of big bills are all knowable, and where a bad week can still be fixed by collecting faster, delaying a purchase, or drawing a credit line deliberately instead of desperately.

The forecast is not a budget. A budget says what you intend; a forecast says what the calendar and your customers' payment habits will actually do to the bank balance, week by week.

Build the forecast in six steps

One row per week, four columns: starting cash, cash in, cash out, ending cash. Ending cash becomes next week's start.

Anchor on the real starting balance. Today's reconciled bank balance — not the balance your books hope for. Every error downstream starts here if this is wrong.
Schedule inflows by expected payment week. Receivables land when customers actually pay, not when invoices say due. Use each customer's real habit: the one who pays in 45 days goes in the 45-day week.
Schedule the known outflows by their real weeks. Payroll Fridays, rent on the 1st, loan payments, quarterly tax estimates, annual insurance in its actual month. Recurring bills go in at their amounts, not averages.
Add a variable outflow line from recent actuals. Fuel, materials, supplies — use the average of the last 8–13 weeks, adjusted for work already booked.
Find the low point. The minimum ending balance across the 13 weeks is the number that matters. Every decision — hiring, buying, drawing credit — is made against that week, not the average.
Roll it weekly. Each week: replace the forecast week with actuals, add a new week 13, and re-read the low point. Ten minutes, same time as your expense entry.

Forecast honesty rules

Three rules keep a forecast from becoming fan fiction. Never move an inflow earlier to make a week look better — if anything, push habitual late payers later. Keep a 'known unknowns' note on the page: the big receivable you are not sure lands in week 6 or week 9 gets modeled in week 9. And forecast only from the reconciled balance — a forecast built on unproven books inherits every error the reconciliation has not caught yet.

Worked example: four weeks of a rolling forecast

A services business starts with $9,200 in the bank. Week 4 carries a quarterly tax payment — exactly the kind of bill this method exists to see coming:

Week	Cash in	Cash out	Ending cash
Start			$9,200
Week 1	$6,800	$5,450	$10,550
Week 2	$5,900	$7,300	$9,150
Week 3	$7,400	$5,100	$11,450
Week 4 (quarterly taxes due)	$6,200	$8,900	$8,750 — the low point

Acting on the low point

A low point is not a problem — it is a deadline for decisions. The standard moves, in order of preference:

Pull inflows forward: invoice earlier, ask for deposits on big jobs, offer a small prompt-payment discount to the chronically late.
Push outflows back honestly: schedule discretionary purchases after the low week; ask vendors about terms before you need them.
Arrange credit while the balance is high: a line approved at $11,450 is cheaper and easier than one begged for at the low point.
If the low point is negative, the forecast just paid for itself — you have weeks to fix what a bounced payroll would have announced in a day.

The forecast, pre-built into a CFO routine

The $59 Virtual CFO Toolkit includes a 12-month Cash Flow Forecast alongside Budget vs. Actual, a KPI Dashboard, AR Aging and Collections, a Break-Even and Pricing sheet, and a CFO Monthly Checklist — the forecast as one pane of a monthly finance routine, in Excel and Google Sheets.

Get the Virtual CFO Toolkit — $59 Break-Even Calculator Guide

Frequently asked questions

How is this different from a budget?

A budget allocates intention — what you plan to spend by category this year. A forecast predicts timing — what the bank balance does each week given due dates and payment habits. Businesses fail on timing with a fine budget on the wall.

What if my income is irregular?

Irregular income is the strongest case for this method: schedule only confirmed inflows in their realistic weeks, and let the low point tell you how much reserve the irregularity requires.

How accurate does it need to be?

Directionally honest beats precisely wrong. If the low point is within a few hundred dollars of reality each month, the forecast is doing its job — it exists to trigger decisions, not to win guessing contests.