Practice Cash Runway Calculator
Six months of cash in one panel: what comes in, what goes out, and where the floor is.
Most practice cash problems are timing problems: fees arrive later than invoices, while payroll leaves on schedule. This steady-state forecast assumes the same fees were invoiced before and during the next six months. Debtor days inform the working-capital estimate, but do not move the cash line. Enter monthly invoicing, payroll, overheads and quarterly VAT to see when cash may break your safety floor.
Debtor days shift every invoice to the right. The forecast is the gap between that shifted line and the costs that do not move.
Calculator
Change any figure and the result updates. Nothing is stored or sent anywhere. Defaults are illustrative.
Starting point
Monthly
VAT
Runway
| Month | In | Out | Balance |
|---|---|---|---|
| M1 | £120,000 | £100,000 | £200,000 |
| M2 | £120,000 | £145,000 (VAT) | £175,000 |
| M3 | £120,000 | £100,000 | £195,000 |
| M4 | £120,000 | £100,000 | £215,000 |
| M5 | £120,000 | £145,000 (VAT) | £190,000 |
| M6 | £120,000 | £100,000 | £210,000 |
Stays above the floor. About £197,368 of fees is tied up in debtors at 50 days; cutting that by 10 days releases roughly £39,474.
Fee inputs exclude VAT; the forecast includes entered VAT payments. Figures are rounded to the nearest pound.
What it assumes
A steady-state practice, so the forecast shows timing, not growth.
The calculator assumes the practice has invoiced at the same monthly level before and during the forecast, so cash collected each month equals fees invoiced. Debtor days do not shift the cash line under that steady-state assumption; they set the separate working-capital estimate. Payroll and overheads go out every month; the VAT payment lands every third month from the month you choose. It shows six months, the lowest balance and the first month that breaks your safety floor.
It also shows the working capital locked in debtors: monthly invoicing multiplied by debtor days and divided by 30.4. Reducing debtor days is usually the cheapest cash available to a practice. For the full method, including pipeline at weighted value and a 13-week weekly view, see cash flow forecasting for architecture practices.
Three levers
Invoice timing, debtor days and the VAT plan move the line more than cutting costs.
- Invoice on the day the stage completes.Waiting for month end adds up to 30 days to every fee.
- Cut debtor days.Statement on day 1, call on day 30, statutory interest in the terms. See stage-based invoicing.
- Plan for the VAT quarter.Set the money aside monthly so the quarter is not a shock. HMRC payment dates are fixed; your invoicing dates are not.
Questions practices ask
Short answers to the questions behind this calculator.
How many months of cash should an architecture practice hold?
Enough to cover the gap between invoicing and collection plus a safety floor. Many practices aim for two to three months of costs, but the right figure depends on debtor days and how lumpy stage invoicing is.
What are debtor days?
The average number of days between issuing an invoice and receiving payment. At 50 debtor days, nearly two months of fees are always outstanding.
When is VAT due?
A VAT return and payment are usually due one calendar month and seven days after the end of the VAT period, per GOV.UK. Check your own scheme and dates.
Does this replace a proper cash-flow forecast?
No. It shows timing on a steady-state practice. A full forecast adds each invoice by expected payment date, pipeline at weighted value, PAYE dates and one-off costs.
Where Avoice fits
Avoice builds the cash forecast from the real invoices and their expected payment dates, synced with Xero or QuickBooks, with the VAT and payroll dates on the same line and a safety floor you set.
The Cash page shows the bank balance, what is expected in the next 30 days and which invoices are overdue. To see it on your own projects, book a demo.