How far ahead should a cashflow forecast go?

Thirteen weeks, updated weekly, is the working horizon for most small businesses. It covers a full quarter, so it captures a VAT payment, three payroll runs and usually one lumpy annual bill such as insurance or Corporation Tax. Anything shorter and you find out about a problem too late to fix it cheaply; anything longer becomes guesswork you stop trusting. A twelve-month version is still worth keeping for planning and for lenders, but it is a different document with a different job. The thirteen-week one is the one you actually make decisions from.

Can I charge interest on late payments, and is it worth doing?

You can. Statutory interest on overdue business-to-business invoices runs at eight percentage points above the Bank of England base rate, which is 11.75% at a base rate of 3.75%, and you can add a fixed recovery sum of £40, £70 or £100 depending on the size of the debt. On a £12,000 invoice paid 45 days late, the interest alone is £173.84. In practice most owners never invoke it with a good customer, and that is a reasonable commercial call. The value is usually in the serial late payer knowing the right exists and that you are willing to use it.

My business is profitable but I'm always short of cash. What's going on?

Profit and cash are measured on different clocks. Profit records a sale when you invoice it; cash records it when the money lands, which on 30-day terms collected in 47 days is a month and a half later. Meanwhile stock, work in progress, VAT you are holding on HMRC's behalf and repayments of capital on a loan all consume cash without touching your profit figure. A growing business is the worst case: every extra sale funds itself out of your bank account first. The fix is a forecast that tracks cash movements rather than accounting profit.

What's the difference between a cashflow forecast and management accounts?

A cashflow forecast looks forwards and answers one question: will there be enough money in the bank in week nine? Management accounts look backwards and answer a different one: is the business actually making money, and where? You need both, because each hides what the other shows. A business can be trading profitably and still run out of cash, and a business can be sitting on a healthy balance because it has not paid its VAT yet. Run monthly management accounts alongside a weekly forecast and the two together tell you the truth.

Cash is getting tight. What should I do first?

Work out the exact date, not the general trend. Build the thirteen-week view, find the lowest closing balance and count how many weeks away it is, because everything else depends on that number. Then go at the debtors list first: it is your money, it costs nothing to collect and it is usually faster than any facility. Talk to HMRC early if a tax payment is the pinch point, since a Time to Pay arrangement agreed before a deadline is far easier to obtain than one requested afterwards. Approach a lender with a forecast in hand, not without one.

Why cashflow visibility matters when growth stalls

Reacting to: UK economy tipped to stall as Iran war chokes growth (City A.M.) →

City A.M. reports that the UK economy is expected to have flatlined again in May, with forecasters pencilling in growth of around -0.1% to zero, following a 0.1% contraction in April. That is a marked slowdown from 0.3% growth in March and 0.4% in February. The report points to the conflict involving Iran as a key driver, pushing up fuel and energy costs and weighing particularly on services, while construction and manufacturing offered some offsetting growth in April.

The bit that should worry small businesses most

Buried in the report is a warning from food industry leaders that food inflation could spike “by as much as 10 per cent later this year” as a result of the conflict's effect on costs. Deutsche Bank's Sanjay Raja described services activity as “sluggish” through May, calling out finance, professional services and real estate as areas of weakness. Chancellor Rachel Reeves acknowledged the impact directly, saying it “was not a war we wanted or joined, but one that will have an impact at home.”

Why this is a cashflow story, not a headline number

A stalling economy does not arrive as a single dramatic event. It arrives as margin quietly eroding, supplier prices creeping up faster than you have adjusted for, and customers taking a fortnight longer to pay because they are feeling the same squeeze. None of that is visible from a bank balance, because a bank balance tells you about the past and says nothing about the £22,000 payroll run sitting eleven days away.

Borrowing your way through it is more expensive than it was through most of the 2010s. The Bank of England base rate is 3.75%, held at the Monetary Policy Committee's most recent meetings, and overdraft and facility pricing sits well above that. The cheapest money in a squeeze is almost always the money you are already owed.

The thirteen-week cashflow, and why thirteen

Thirteen weeks is one quarter, and a quarter is the natural unit for a UK business because it is the rhythm the tax system already runs on. A VAT quarter's payment falls one calendar month and seven days after the period ends. Corporation Tax falls nine months and one day after the year end. Payroll falls on the same date every month. Thirteen weeks is long enough to see those collide and short enough that you can still do something about it.

Weekly matters more than the length. A monthly forecast averages away the fortnight that actually hurts, and the fortnight is where businesses fail.

Worked example: the quarter that looks fine and isn't

Illustrative figures throughout. A services business turns over £480,000, invoicing around £40,000 a month. It has £38,000 in the bank on 1 August and £96,000 owed to it, collected on average in 47 days against 30-day terms. Fixed monthly outgoings are £22,000 payroll, £2,800 rent and £6,400 of other overheads — £31,200 a month. A VAT bill of £14,800 for the quarter ended 31 July falls due on 7 September, and Corporation Tax of £21,000 falls due on 1 October.

Opening balance, 1 August: £38,000.
August — receipts £42,000, overheads £31,200. Closing: £48,800.
September — receipts £38,000, overheads £31,200, VAT £14,800. Closing: £40,800.
October — receipts £41,000, overheads £31,200, Corporation Tax £21,000. Closing: £29,600.

Across the quarter the business is £8,400 down and still holds £29,600. Read monthly, nothing about that is alarming. But the money does not arrive evenly. Corporation Tax leaves on 1 October. Payroll leaves on the 28th. October's receipts are weighted to the end of the month because September's invoices went out on the 30th. Run the same figures weekly and the picture changes: by 28 October the business has taken in £23,000 of its October receipts, paid £21,000 of Corporation Tax and £9,200 of non-payroll overheads, and then pays £22,000 of wages. The balance bottoms out at £11,600, four days before it recovers to £29,600.

Eleven thousand pounds is a fortnight in which one customer paying late, or one van needing replacing, is the difference between fine and phoning the bank. Nobody looking at the monthly summary would have seen it.

The three levers, in the order they actually work

Collect faster. This is the cheapest cash you will ever raise, because it is already yours. On £480,000 of turnover, every day of average collection time is worth £1,315. Pulling the average in from 47 days to 30 releases 17 days of turnover — £22,356 — as a permanent one-off improvement in working capital, and it costs nothing but a process.

Move the timing of what leaves. Not avoiding a bill, but knowing which week it lands in and whether it can sit a week either side without a penalty. Tax bills cannot move, which is exactly why the discretionary ones should.

Protect margin. On £480,000 of turnover, a 2% price adjustment is £9,600 straight to the bottom line if volumes hold. In a period when input costs are rising, holding your prices flat is a decision to absorb someone else's inflation.

What being paid late is actually worth to you

Most owners never invoke their statutory rights, and it is worth knowing what is being left on the table. Under the late payment legislation you can charge statutory interest on overdue business-to-business invoices at eight percentage points above the Bank of England base rate — 11.75% at a base rate of 3.75%. On a £12,000 invoice paid 45 days late that is £173.84.

You can also claim a fixed sum for recovery costs, set by the same legislation: £40 on debts under £1,000, £70 between £1,000 and £9,999.99, and £100 on debts of £10,000 or more. And if an invoice genuinely goes bad, VAT bad debt relief lets you reclaim the VAT you have already handed over — £2,000 on that £12,000 gross invoice — once the debt is more than six months overdue and has been written off in your refunds for bad debts account. The claim window runs for four years and six months from the later of the date payment was due and the date of supply.

You will not want to charge interest to your best customer. You will want the serial late payer to know you could.

The five-line version you can build this week

Open a spreadsheet with thirteen columns, one per week, starting this Monday.
Line one: opening bank balance. Take it from the bank, not from your accounts.
Line two: money in. Go through the aged debtors list invoice by invoice and put each one in the week you genuinely expect it, not the week the terms say.
Line three: money out. Payroll, rent, loan payments, direct debits, and every tax date — VAT one month and seven days after the quarter end, PAYE by the 22nd, Corporation Tax nine months and one day after the year end.
Line four: net movement. Line five: closing balance, which becomes next week's opening balance. Then look for the lowest number in row five, because that week is your business's real financial position.

Update it every Friday in ten minutes. A forecast that is rebuilt from scratch each quarter is an exercise; one that is nudged weekly is an instrument.

Where this fits

We cover the mechanics in more depth in how to read a cashflow forecast and in our cashflow forecasting guide, and it is the discipline we build into management accounts for clients — monthly reporting with commentary that shows where the pressure is building, rather than confirming it after the event. If the forecast is telling you something you do not like, cashflow and budgeting work is about changing the answer rather than watching it. Periods of genuine uncertainty are exactly when that visibility earns its keep.

The economy is stalling — here's why cashflow visibility matters more now