Why a forecast matters more than a P&L in the short term

Your profit and loss account tells you whether the business made money over a period. It doesn't tell you whether you'll be able to pay the wages in three weeks' time. Those are two different questions, and it's entirely possible for the answer to the first to be "yes" while the answer to the second is "not without a very uncomfortable conversation with the bank." Cash gets tied up in stock, in unpaid invoices, in a VAT bill landing at an awkward moment — none of which shows up as a problem on a profit and loss account, but all of which can genuinely stop a profitable business from being able to pay its bills.

A cashflow forecast is about timing, not profitability. It answers a narrower but more urgent question: when is money actually expected to land in the bank, and when is it expected to leave, so you can see the gaps before they open up rather than after.

Why 13 weeks

An annual budget is useful for direction. It's far too blunt an instrument for spotting a cash squeeze that might hit in four weeks' time. A rolling 13-week forecast sits in the sweet spot — long enough to see genuine trouble coming with time to act, short enough that the numbers going into it are grounded in things you actually know (confirmed invoices, known bills, contracted payroll) rather than guesswork. "Rolling" is the important word: as week one closes, you drop it off and add a new week 13 onto the end, so you always have the same three-month runway in view rather than watching the horizon shrink toward a fixed year-end.

The structure: what goes in a 13-week forecast

Keep the structure simple. A spreadsheet with one column per week and the following rows is enough to get real value from it:

  • Opening balance — what's actually in the bank at the start of the week. Week two's opening balance is simply week one's closing balance carried forward.
  • Confirmed income — invoices already raised, with a payment date you're genuinely confident about, not just the due date on the invoice.
  • Expected income — income you're reasonably confident about but haven't yet invoiced, or invoices where payment could slip. Keep this separate from confirmed income so you can see how much of your forecast is solid ground and how much is an assumption.
  • Fixed outgoings — rent, salaries, loan repayments, subscriptions, anything that happens regardless of how trading goes that week.
  • Variable outgoings — stock purchases, one-off supplier payments, anything tied to activity levels rather than a fixed schedule.
  • Closing balance — opening balance plus all income, minus all outgoings, for that week.

Add one more line beneath the closing balance: the lowest point the balance is expected to hit within that week, if payments and receipts don't land evenly across the five working days. A healthy Friday closing balance can still hide a genuinely tight Tuesday, and it's the tight Tuesday that actually causes problems.

Building it, week by week

Start with what you know for certain. List every invoice currently outstanding, and put a realistic expected payment date against each one — not the due date, the date you actually expect it based on how that client normally pays. Do the same for fixed outgoings: payroll dates, rent, loan repayments, any regular supplier terms. That's your backbone. Then layer in expected but unconfirmed income, and variable costs you can reasonably anticipate over the coming three months. Total each week, carry the closing balance forward as the next week's opening balance, and you have a working forecast.

The first version will take the longest to build. After that, updating it each week — ticking off what actually happened against what you predicted, and extending the rolling window by one more week — should take a fraction of the time, and it's this weekly discipline that makes the difference between a forecast that's useful and one that's a one-off exercise nobody looks at again.

Reading it once it's built

Don't get lost in the detail of every line. Focus on the closing balance trend across the 13 weeks: is it broadly stable, climbing, or steadily eroding? A single tight week isn't necessarily a problem if it recovers the week after. A closing balance that quietly shrinks week after week for a month is telling you something important, even if no individual week looks alarming on its own — and catching that trend in week three gives you far more room to act than spotting it in week eleven.

Where forecasts usually go wrong

Two mistakes come up more than any others. The first is treating the forecast as a one-off document — built once in a burst of good intentions, then never revisited, so by week four it's more fiction than forecast. The second is being too optimistic on timing: assuming every invoice gets paid exactly on its due date, when in reality a portion always lands late. Building in a realistic buffer for late payment, based on how your clients actually behave rather than what your payment terms say they should do, makes the forecast far more useful when it actually matters.

Turning the forecast into decisions

A forecast that only the accountant looks at isn't doing its job. Its real value is in the hands of whoever's making the day-to-day calls — deciding whether now's the right time to place a big stock order, whether a supplier payment can wait a week, or whether it's worth chasing a slow-paying client a little harder this month rather than next. Used properly, a rolling forecast turns cash management from something you react to into something you can see coming and plan around.

How Buzz helps

This is exactly the kind of visibility we build into management accounts — regular cashflow reporting sitting alongside profit and loss, reviewed on a proper rhythm rather than built once and left to go stale. If your current view of cashflow is a spreadsheet nobody's opened in months, or you'd rather have someone build and maintain the rolling forecast for you, book a free discovery call and we'll talk through what that would look like for your business.