How to Forecast a Cash Gap in Your Business

Distinguish a cash flow from a P&L

A profit-and-loss account records when revenue is earned and costs are incurred. A cash-flow forecast records when money actually enters and leaves the bank. A company can be profitable and cash-negative simultaneously — for example, if it invoices in advance of receiving payment while paying suppliers on shorter terms.

The cash-gap forecast is concerned only with cash: when invoices are likely to be paid based on customer payment behaviour, and when outgoings — payroll, PAYE, VAT, rent, supplier payments — will actually clear the account. Build this on timing, not accrual accounting.

Start from your current bank balance

Open your forecast with the actual cleared bank balance as of today — not the book balance in your accounting software, which may include uncleared items. From that starting point, map out expected inflows and outflows week by week for the next 13 weeks.

Inflows: list each debtor, their outstanding balance and their historical payment pattern. If a customer typically pays at day 45 regardless of your net 30 terms, model them at day 45. Optimistic timing assumptions are the single most common reason cash-gap forecasts fail to predict actual shortfalls.

Map every outflow with precision

Fixed outflows are straightforward: rent, loan repayments, hire purchase instalments, and standing orders all fall on known dates. Variable outflows require judgement: payroll is typically known several weeks ahead; supplier payments depend on your creditor terms and current balances; VAT and PAYE fall on quarterly and monthly schedules respectively.

Include one-off items that are foreseeable: a capital purchase scheduled for week six, a tax payment due in week ten, or a large customer order that will require raw material procurement in week two. These are the items most commonly omitted from cash forecasts and most likely to create a surprise gap.

Identify the gap and its size

Sum inflows and outflows for each week. The running balance column will show you whether and when the balance goes negative, and by how much. This is your cash gap: the date it begins, the depth of the trough and the date the balance recovers (if it does within the forecast horizon).

Run a downside scenario: what happens if your two largest debtors each pay 10 days late? What if a planned customer payment falls into the following month? A downside scenario that pushes the gap deeper or earlier is normal — the question is whether the worst-case gap remains manageable with available facilities or whether you need to plan additional headroom.

Act on the forecast, not the gap

A cash-gap forecast is only valuable if it drives action. If the model shows a £120,000 trough in week nine, the response options include: accelerating collections on the largest debtors now; deferring a discretionary capital purchase; drawing on an existing revolving credit facility; or approaching a lender for short-term working capital support.

The critical point is timing. Approaching a lender eight weeks before a projected gap, with a forecast in hand that clearly explains the gap and the repayment route, is a very different conversation to approaching them in the week the account hits zero. Lenders respond to preparation; they are cautious about distress.