A rolling 13-week cash forecast from your books

How to build a rolling 13-week cash forecast from your aged debtors, bills, payroll and orders, and when a business needs one instead of a monthly view.

By Achekam · 11 October 2026 · 5 min read · For Running a business businesses in South Africa, Nigeria, Kenya

A monthly forecast tells you the account will be fine at the end of March. It does not tell you that payroll leaves a few days before the large customer pays, and that for those few days the business is overdrawn beyond its limit. Cash problems happen in weeks, sometimes in days, and a monthly view smooths them out of sight.

A rolling 13-week forecast is the tool for that problem. It looks one quarter ahead, week by week, and it is rebuilt every week so the horizon never shrinks. It is built from figures already in your books, and keeping it current is quicker than building it.

Weekly for 13 weeks, monthly for 12 months

ICAEW notes that rolling weekly cash forecasts for 13 weeks ahead are often used in turnarounds, and that rolling monthly forecasts for the next 12 months are usually necessary. It adds that both are often required for loan applications.

The two do different jobs:

Forecast	Horizon	What it is for
Rolling weekly	13 weeks	Day-to-day cash control: which payments to time, when to chase, whether the overdraft will hold
Rolling monthly	12 months	Planning: seasonality, large purchases, funding needs, the bank's view

You need the weekly one when cash is tight, when the business is growing fast or changing, when a large customer's payment timing could tip the balance, or when the bank asks for it. A business with comfortable cash and steady trade may manage on the monthly forecast alone, checking weekly only in its tight season.

The direct method, in plain language

ICAEW recommends using the direct method where possible: showing cash coming in and going out in language non-accountants understand, and clearly documenting the assumptions. It notes that the indirect method, which starts from profit, is harder to follow, although it is a useful check.

In practice, the direct method is a grid. Weeks run across the top. Down the side:

opening bank balance;
receipts: customers, by name for the large ones; cash and card sales; anything else;
payments: suppliers; payroll and its taxes; rent; loan repayments; VAT and other taxes; capital purchases;
net movement for the week;
closing bank balance, which becomes next week's opening.

ICAEW's list of inputs for a cash forecast includes turnover, cost of sales, how long you take to pay suppliers and how long customers take to pay you, inventory needs, rent dates, capital spending, and tax and loan repayments. Each of these becomes a row.

Receipts from the aged debtors

Start with what customers already owe. Achekam ages receivables into 0-30, 31-60, 61-90, 91-120 and over 120 days, with overdue totals, which gives you the list to forecast from.

ICAEW advises keeping detailed data behind cash forecasts, particularly for debtors: expected, worst-case and best-case dates; maximum, expected and minimum amounts; the probability of collection; and a named person responsible for each item. For a small business, a workable version is:

List every customer balance above a level that matters to you.
For each, write the week you expect payment, and the week it arrives if they are late as usual.
Put the expected week in the forecast, and keep the late week in a note beside it.
Put a name against each large item: the person who will chase it.
Add forecast new sales only for what will be both invoiced and collected inside the 13 weeks.

Payments: suppliers, payroll and committed orders

Next, list what you must pay.

Suppliers. Supplier bills recorded in Achekam line by line with VAT, and paid in full or in parts, give you what is already owed. Place each in the week you will actually pay it, not the week it falls due if you usually pay later.

Payroll. Each approved pay run in Achekam has a payment schedule downloadable as CSV. Marking it paid only records the fact; Achekam moves no money. The schedule shows what goes out on payday, and the taxes and deductions that follow on their own due dates.

Committed orders. With procurement in use, approved purchase orders count as committed spend against budgets, and the screen shows budget, spent, committed and available for each expense account and period. Committed orders are payments you have already agreed to make; place them in the weeks the goods are expected and paid for.

Everything else. Rent, loan repayments, VAT, insurance and any capital purchases, each in its week.

Start from the reconciled bank balance

A forecast that starts from the wrong balance is wrong in every week. The opening figure should be the bank balance as reconciled, not as shown in an unreconciled ledger.

In Achekam, bank statements are imported as PDF, CSV, Excel, OFX, QIF, MT940 or CAMT.053, and each import is checked so that the opening balance plus movements equals the closing balance. Bank lines are matched by suggestion and a person accepts each match, and a reconciliation completes only when every line is matched or explained. Use the reconciled closing balance as week one's opening, and note any uncleared payments separately.

Rolling it forward each week

ICAEW advises producing worst-case, most-likely and best-case scenarios, including a prediction of the earliest date extra funding may be needed, and checking forecasts against actuals to improve the process. A weekly routine:

Replace last week's forecast with what actually happened.
Note the biggest difference, and why it happened.
Drop the finished week and add a new week thirteen.
Update receipts from the latest aged debtors and payments from the latest bills.
Look at the worst-case line. If it dips below your overdraft limit, act now: chase, delay a purchase, or talk to the bank.

For businesses with seasonal swings, planning cash for the low season shows the monthly view at work.