Every tool so far explains the past. This one protects the future. The 13-week cash forecast is a week-by-week projection of money in, money out, and the resulting bank balance, one quarter ahead. Turnaround specialists build it first when they walk into a distressed company — because it's the instrument that shows, to the week, when the business runs out of oxygen. Healthy businesses run it for the same reason pilots check fuel before takeoff, not after the engine sputters.
Why 13 weeks? Long enough to see around the corner — the quarterly tax payment, the seasonal dip, the insurance renewal. Short enough to stay concrete: you genuinely know most of what happens in the next 90 days. And weekly, not monthly, because months average away the danger: a month can look fine in total while week two of it can't make payroll. Cash problems are week-shaped.
Columns: the next 13 weeks. Rows:
1. Starting cash. Week one = actual bank balance today (all operating accounts). Every later week = the prior week's ending cash.
2. Cash in — when it lands, not when it's earned. Known collections (invoices outstanding, by their realistic pay date — the AR aging plus honesty about each customer's habits), recurring receipts (subscriptions, retainers, autopays, by their actual arrival week), and a conservative estimate for not-yet-booked sales (base it on your typical weekly collections, haircut it — this is a survival tool; optimism belongs in the sales meeting).
3. Cash out — every dollar with a date. Payroll on its weeks (the big rock — place it first), rent, loan payments (full payment, principal included — the P&L's opinion is irrelevant here), insurance, software, supplier bills by due date, credit-card payment, tax remittances (sales tax, payroll deposits, quarterly estimates — the ambush-shaped ones), and your own draw, honestly.
4. Ending cash = start + in − out. The row you actually read: thirteen numbers marching right. If any week's number goes negative — or below your minimum comfort line — you've found a future crisis while it's still cheap to fix.
Build it in a plain spreadsheet in an hour or two. Don't gold-plate it; a rough forecast maintained weekly beats a beautiful one abandoned by March.
The forecast's product is one sentence: "Week 9 is the problem." Cash dips under payroll the week the quarterly estimate and the insurance renewal collide. Today — eight weeks early — that's a solvable puzzle with many moves: chase two big invoices now (offer a small prompt-pay incentive if needed), shift a discretionary purchase two weeks, ask the supplier for net-45 on one bill, pre-arrange to draw on the line of credit, trim your own draw for a month. The same discovery in week 9 has exactly one move: panic — emergency borrowing at bad terms, bounced payroll, or the call you never wanted to make. Distance is options. The forecast is a machine for buying distance.
It also disciplines growth decisions: the hire, the equipment, the marketing push each get typed into the sheet first — if ending cash survives all 13 weeks with the new spending in it, proceed; if week 11 goes red, the answer is "not yet" with a date, not "no." (This is the float check the CAC-payback lesson keeps pointing at.)