How to build a cashflow forecast that doesn't break by month 3
A practical guide to building a cashflow forecast from real bank and ERP data, without the usual Excel sheets that drift out of sync.
Most cashflow forecasts start strong in month one and fall apart by month three. It's rarely the formulas — it's the data. If your model depends on someone pasting bank balances into a spreadsheet every Friday, the model dies the first Friday nobody does it.
What a cashflow forecast really is#
An honest cashflow forecast answers one question: how much cash will be in the bank X weeks from now? It's not a P&L, it's not a budget — it's a projection of your checking account.
For it to work you need three layers:
- Starting point: your current balance, consolidated across all banks.
- Expected inflows: invoiced receivables and likely recurring revenue.
- Expected outflows: scheduled payments, payroll, taxes, recurring expenses.
Why Excel breaks#
The problem isn't Excel — it's manual updates. Each data source (bank, ERP, Stripe, Shopify) lives somewhere different and runs on its own cadence. If your forecast assumes someone copy-pastes every Friday at 9am, you have a brittle system.
The three most common mistakes#
- Mixing accrual and cash. An issued invoice is not cash. A sale invoiced on 60-day terms affects cash in 60 days, not today.
- Not modeling the real collection cycle. If your customers pay in 45 days instead of 30, the whole forecast shifts by 15 days.
- Ignoring small recurring expenses. SaaS subscriptions, bank fees, quarterly taxes — added up, they weigh more than they look.
A forecast that doesn't update itself isn't a forecast. It's a stale photo.
The alternative: connected data#
The fix isn't a better Excel template. It's connecting the sources directly. When the bank balance refreshes every hour, when every invoice is tagged with its probable collection date, when every scheduled payment shows up automatically — the forecast stops being a weekly exercise and becomes a dashboard you check when you need it.
NextScenario does exactly that: connects your banks via PSD2, your ERP via API, and your sales channels, and builds the forecast in real time.
How to get started#
If you want to build it yourself, start minimal: a sheet with 13 weeks of projection, real starting balance, confirmed inflows and outflows. Ignore speculation. Update every Monday.
If you'd rather it update itself, book a demo and we'll show you how to get live in under a day.