Most companies do not fail because the founder was wrong about cashflow. They fail because something landed in a month nobody had looked at. Waterline models cash runway by tracking payroll, purchase orders, projects, drawdowns and cost share on the month cash actually moves, and shows the month you cross the waterline.
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Every founder has a folder with plan-v3-FINAL-actually.xlsx in it. The reason is not disorganisation — a spreadsheet has no way to hold two versions of the truth at once.
Each figure is that change applied to the whole model. Keep one, discard it, or hand it to somebody.
A scenario changes nothing until you apply it. Your co-founder is not watching you model redundancies in real time.
Extending a period moves the spend, the billing, your share’s deadline and every milestone that depended on them. You see all of it, not the one number you thought to check.
Your fractional CFO builds a scenario in your model and offers it. You accept or decline. Advice arrives as a thing you can run rather than a paragraph in an email.
Knowing a month breaks is half of it. The other half is finding out, in ninety seconds, which of the three things you could do about it actually helps.
Connected to your books. Months you have closed use actuals; the projection starts where the ledger stops. A warning from a stale model is worse than none.
Uncovered commitments, milestones after the cash, a runway resting on money nobody promised. Two alerts at most, worst first.
Build the change as a scenario, see what it does to the whole model, apply it or throw it away. The live plan does not move until you say so.
A federal award, a prime contract you sit under, a joint venture where each partner carries a share, a project split across three funders with three different rules. They look like different arrangements and they behave like one: you spend first, you bill on somebody else's rhythm, you wait, and part of the cost never gets reimbursed at all.
Every other runway tool assumes money lands when somebody decides to send it. Waterline assumes it lands when the paperwork says it does.
The weeks between sending an invoice and the money landing are where a fully funded organization runs out of cash. Whether the payer is an agency, a prime, or a JV partner with their own approval chain, the arithmetic is the same. Set it once per arrangement.
Cost share on an award. Your contribution to a joint venture. The unfunded portion of a split-funded project. Different words, one behaviour: it accrues against what you bill, it has a deadline, and it is money you have promised somebody and have to find.
A no-cost extension, a contract mod, a JV milestone that slips a quarter. The budget spreads thinner, your share's deadline moves with it, and payment in arrears arrives later — the half people forget.
Each rhythm changes when the money comes in and when your share falls due. Waterline schedules both on the rhythm you actually bill, not on a calendar it invented.
Your share, owed · two periods
It rises with what you bill, not with the calendar. The dashed rules are the moments somebody checks it.
Also modelled Indirect and negotiated rates · restricted funds that stay restricted · drawdown schedules · milestone billing · pass-through to subrecipients · multiple funders on one project, each with their own period and rules.
And if you work with federal awards SF-424A imports and exports — categories, periods and rates read straight in, and a budget that goes back out in the shape the agency expects. Nobody retypes anything.
If none of your money arrives that way, ignore all of it — the rest of the product does not depend on it. If some of it does, this is the only runway tool that has heard of any of this.
A purchase order payable in month nine changes nothing about when the cash runs out. It still commits you. Both numbers, never confused.
An unreimbursed share falling due after your cash runs out is money you have promised a funder, a prime or a partner and do not have. It is invisible in every budget document you own.
A projection can go negative in January and recover in March when a reimbursement lands. A company with no cash in January does not reach March.
A project ahead of pace runs out of budget before it runs out of months — and whoever is paying does not cover the overrun. You do.
Runway 5.6 months committed, 12.4 with speculative on. That is not a longer runway. It is a dependency with a size.
Board dates, certifications and pilot deliveries plotted against the balance that has to last until them.
Software that lists everything that could go wrong becomes unreadable in a week, which leaves you worse off than before you installed it. At most two alerts per screen, worst first, each naming the thing to look at rather than the feeling to have.