Cash flow forecasting: a practical guide for finance leads

Cash flow forecasting is the instrument a business uses to safeguard its ability to pay: for a defined period it sets expected cash receipts against expected payments and shows whether the balance is sufficient at all times. Unlike the profit-and-loss account, it does not care whether a deal is profitable — only when the money actually moves. That timing is what decides whether an otherwise healthy company runs into a squeeze.

This guide sets the topic out from the ground up: what a cash flow forecast does, which methods and horizons exist, how to build a reliable forecast step by step, and when a spreadsheet is enough versus when software is the better choice.

What cash flow forecasting is — and why it matters

Liquidity is the ability to meet payments as they fall due. A cash flow forecast makes that ability plannable: it projects future cash movements and the resulting bank balance so a shortfall becomes visible before it happens. The principle behind it is simple — a business does not run out of money because of losses, but because at a particular moment the cash isn’t there.

The difference between profit and cash is the heart of the whole exercise. A company can show black figures in its management accounts and still get into payment difficulties, because receivables come in later than planned, capital is tied up in stock or work in progress, or a large payment falls due before the matching receipt arrives.

Two jobs come first. The first is to safeguard solvency: the forecast makes sure there are always enough funds to cover payroll, suppliers, tax and loan repayments. The second is to spot squeezes early: it shows the lowest point of liquidity before it is reached — often weeks ahead, while there is still room to act.

Direct and indirect methods

There are two basic methods for forecasting cash flow. They differ in their data basis — not in their goal.

The direct method plans cash movements directly: it lists expected receipts (customer payments, deposits, other inflows) and expected payments (payroll, suppliers, tax, rent, loan repayments) individually and nets them off per period. The result is tied straight to actual payment dates, which makes it the basis of all short-term control. For the week-by-week view, there is no way around the direct method.

The indirect method instead starts from net profit in the income statement and works it back to a cash figure via non-cash items (depreciation, provisions) and changes in working capital. It sits closer to the accounts and suits the medium- and long-term view — for short-term cash control it is too coarse.

In practice the two complement each other: the direct method steers day-to-day operations, the indirect one links cash to profit and balance-sheet planning. For the operational 13-week outlook this guide focuses on, the direct method is the standard.

Short-, medium- and long-term horizons

Which period makes sense depends on the question the forecast should answer. Three horizons have become established in practice.

The short-term forecast covers the coming weeks. Its standard is 13 weeks — a full quarter, week by week, based on actual cash movements. This horizon is long enough to see squeezes in time and short enough to stay reliable. It is the operational steering instrument for management; the 13-week liquidity plan guide explains its structure and logic in detail.

The medium-term forecast looks beyond the quarter, usually across 13 months in monthly slices. It links operational cash to budget and annual planning, shows seasonal patterns and the effect of planned investments — see the 13-month plan. Here the indirect method is often used, because the figures are derived from profit planning.

The long-term forecast spans several years and serves strategic financing — large investments, repayment structures, capital needs. It works with coarser assumptions and is not a tool for day-to-day control.

Crucially, the short-term forecast should be kept rolling: each week the elapsed period drops off and a new one is added at the end, so the horizon stays constant and the numbers never age.

How to build a cash flow forecast step by step

A reliable forecast comes together in four steps. What matters is that it rests on real data rather than gut estimates — otherwise the prettiest table is worthless.

Step 1 — gather your data sources. The quality of the forecast stands or falls on the input data. Four sources form the foundation:

• Open-item lists (receivables and payables): they show which invoices are still outstanding and when they fall due — the most reliable basis for the weeks ahead.
• Current account balances: the starting balance everything builds on.
• A consolidated bank view: across all accounts and credit lines. With several banks, the true available balance is in no single online-banking screen; the bank overview guide shows how to put it together.
• Recurring payments: payroll, rent, leasing, insurance, tax instalments, loan repayments — plannable and dateable.

Step 2 — build the table. Lay out a grid: rows for receipt and payment categories, columns for the periods (weeks or months). Each period follows the same logic: opening balance plus receipts minus payments gives the closing balance, which becomes the opening balance of the next period.

The figures above are generic example values. They show the principle: in Week 3 the balance slips below zero, even though the three weeks are positive in total. Those are exactly the low points the forecast is meant to reveal.

Step 3 — keep categories and assumptions clean. Separate certain items (already-dated open items, recurring payments) from uncertain ones (expected new business). For uncertain receipts, a realistic rather than an optimistic assumption pays off — better to date a payment a week or two later than to flatter the plan.

Step 4 — roll it forward. A forecast is not a one-off document. Update it at least weekly: enter actual payments, extend the horizon by a week, review variances. That turns a snapshot into an early-warning system that gets more accurate every week. How the short-term outlook connects to working capital and the financial status for the bank is covered in their own guides.

Spreadsheet or software — when to switch

The most common practical question is which tool to use. Both have their place; the decision comes down to complexity and frequency.

A spreadsheet is the right way in. It is available everywhere, flexible and free. For small, simple structures with one or two accounts and few open items, it can carry a solid forecast. The price is manual work: balances, open items and payments have to be transferred by hand and the formulas maintained. To get started, use our free template.

Software pays off once manual upkeep becomes the bottleneck — several accounts or banks, several entities, many open items, or when the forecast should roll forward weekly. That is where a solution that pulls the data straight from bank transactions, rather than having them retyped, shows its strength.

This is exactly where LiquidityLens comes in: it builds the 13-week cash flow forecast with AI from your real bank transactions, CSV exports and open items, consolidates several accounts, and rolls the outlook forward automatically. The effort that a spreadsheet demands every week falls away — the numbers stay current without anyone retyping them. Whether that fits your situation is quickest to clarify in a short conversation.

Frequently asked questions

The most important questions on cash flow forecasting are gathered at the end of this page.

Frequently asked questions