Quick question. What's the lowest your bank balance will get between now and the end of next quarter? And which week will it happen?
If you answered both without opening anything, you're either a very unusual owner or you already have a 13 week cash flow forecast. Most people answer the first part with a shrug and the second part with "probably around payroll."
That shrug is what this tool replaces. Below: what a 13-week forecast is, when it's worth the effort, how to set one up, and the 30-minute weekly habit that keeps it honest.
What is a 13 week cash flow forecast?
It's a short term cash forecast built week by week instead of month by month. Thirteen weeks is roughly one quarter: far enough out to see trouble coming, close enough that you can make realistic guesses.
Each week has the same rows: starting cash, cash in, cash out, and ending cash. Every week, you replace the week that just happened with actual numbers and add a new week at the end, so you're always looking 13 weeks ahead. People call this a rolling forecast, which sounds fancier than it is.
Monthly forecasts are great for planning. The problem is that cash rarely gets tight for a whole month. It gets tight for four days between a big payroll and a slow customer. A monthly view averages those four days away. If you want the monthly version first, see cash flow forecast for small business: build one in an afternoon.
When is a 13-week forecast worth it?
Not every business needs one all the time. It earns its keep when:
- Payroll is large compared to your cash balance
- Customers pay on 30, 45 or 60-day terms while you pay staff weekly or biweekly
- You're seasonal and heading into a slow stretch
- You're about to take on a large project with upfront costs
- A lender or investor has asked for one
- Your cash reserve is thinner than you'd like (more on what "thin" means in how much cash a small business should keep in the bank)
What goes in a 13 week cash flow template
A useful 13 week cash flow template has the weeks across the top and these rows down the side:
- Starting cash for the week.
- Receipts, ideally split by your largest customers plus "all other," and placed in the week you realistically expect payment.
- Payroll, including employer payroll taxes, in the actual pay weeks.
- Rent and other fixed bills on their due dates.
- Vendor and supplier payments, based on your A/P aging.
- Loan payments and owner draws.
- One-off items: insurance renewals, equipment, annual software.
- Ending cash, and next to it, your minimum comfortable balance.
- If you have a line of credit, the available amount remaining.
Keep it to one screen if you can. A forecast you can't read at a glance is a forecast you'll stop opening.
A worked example: a cleaning company's first five weeks
Say you own a commercial cleaning company with biweekly payroll of $38,000. Clients pay on 30-day terms, some on 45. Starting cash is $52,000, and your floor is $25,000.
- Week 1: collections $24,000, payroll $38,000, other bills $6,000. Ending cash: $32,000.
- Week 2: collections $30,000, rent and supplies $9,000. Ending cash: $53,000.
- Week 3: collections $18,000, payroll $38,000, other bills $5,000. Ending cash: $28,000.
- Week 4: collections $22,000, other bills $6,000. Ending cash: $44,000.
- Week 5: collections $20,000, payroll $38,000, other bills $5,000, annual vehicle insurance $11,000. Ending cash: $10,000.
Glance at weeks 2 and 4 and the business looks comfortable. Week 5 sits $15,000 below your floor, because a payroll and the insurance bill land in the same slow-collection week. And you know it in week 1.
That gives you four weeks to do something calm: call the two clients on 45-day terms, ask the insurer about monthly installments, or confirm your line of credit is ready. Compare that with finding out on the Thursday before payday.
The weekly update, in 30 minutes
The forecast is only useful if it stays current. Pick a day (Monday morning works for most people) and:
- Enter last week's actual bank balance.
- Compare last week's forecast to what actually happened, line by line.
- Note the biggest miss and why. A customer paid late? A bill was bigger than expected?
- Update upcoming weeks based on what you learned.
- Add week 13 at the end.
- Check the lowest week and decide if anything needs doing now.
Over time, step 3 is where the value builds. You learn which customers are reliable, which costs you underestimate, and how much cushion you actually need.
Who should own the forecast?
The owner should read it every week. Building and maintaining it is usually better handled by someone with finance training and access to clean books, because a forecast is only as good as the reconciled numbers it starts from.
In many small businesses, that's the role of a fractional CFO. If you've wondered what that role involves in practice, what does a fractional CFO actually do all month? walks through it. Our CFO services include building the forecast with you and reviewing it on a set schedule.
Questions owners ask
Why 13 weeks instead of three months?
Thirteen weeks is the same length as a quarter, but weekly detail shows the specific weeks when payroll, rent and slow collections overlap. A monthly view can hide a short, sharp dip in cash.
How accurate is a 13 week cash flow forecast?
The first few weeks are usually quite accurate because they're based on known invoices and bills. Later weeks are rougher estimates. Updating weekly and comparing forecast to actual improves accuracy over time.
Do I need special software for a 13-week forecast?
No. A spreadsheet works well for most small businesses. What matters more is starting from reconciled bank balances and current receivables and payables reports.
Want to see your tight weeks before they arrive?
If payroll weeks make you nervous, we can build a 13-week forecast from reconciled books and review it with you on a regular rhythm. Request a consultation and tell us when cash feels tightest. If you'd like to see a planning range first, the Scope & Investment Estimator on our pricing page is a good starting point.