The thirteen-week forecast is the only forecast a small company needs
Most owner-run companies already have an annual budget, or at least a tax projection their accountant built last spring. Those files answer a different question. They ask whether the year, taken as a whole, will land near a number you can live with. They do not tell you whether the bank account will clear payroll in the third week of March. Cash is a sequence of days. A year is an average of those days, and averages hide the weeks that hurt.
Thirteen weeks is long enough to see a gap forming and short enough that the inputs are still mostly known. You can name the invoices that will be paid, the suppliers who will be paid, the payroll runs, the rent, the GST or HST instalment, and the loan payment. Beyond that horizon the list becomes a set of hopes. People still publish twelve-month cash forecasts. They are useful as a conversation about shape. They are a poor place to park a decision about a facility or a supplier term.
The method is plain. Start with the bank balance on Friday. List receipts you can defend, by week, from open receivables and known retainers. List payments the same way. Keep payroll, rent, tax and debt on their own lines so a quiet sales week does not hide a statutory payment. Roll the close of week one into the open of week two. When the close goes negative, you have a date. The date is the whole point of the file.
Companies that do this well treat the forecast as a weekly habit, not a project. Each Monday someone updates receipts that arrived and payments that cleared, then looks again at week nine. If week nine has moved, they ask why. Often the reason is a single customer who slipped from net 15 to net 45, or a supplier who pulled a delivery forward. Those are phone calls, not strategy sessions. The forecast earns its keep by making the phone call happen while there is still a week to spare.
A common objection is that the business is too seasonal for a short window. Seasonality is exactly why the short window helps. A food wholesaler we have seen in composite work had a nine-day hole every February. The annual budget showed a profitable year. The thirteen-week file showed the same hole arriving on roughly the same date. The fix was terms, not a new operating line. You only find that if you are willing to look at February as February, rather than as a twelfth of a good year.
Another objection is that the numbers change too fast to bother. They do change. That is an argument for a short file you can rebuild in an hour, not for giving up. A model with forty tabs and a colour-coded dashboard will not be touched on a Tuesday morning. A single sheet with thirteen columns will.
We still build annual budgets. They have a job in October, when you are naming hires and leases. For the question “will we make payroll and the CRA instalment without surprising ourselves,” thirteen weeks is the file we open first.
Takeaway: keep a thirteen-week cash sheet current, and treat a negative week as a date you can still act on.