Start with what you know today: your current bank balance. That’s your starting point. From there, you’re going to project forward week by week.

List every expected inflow. Customer payments based on outstanding invoices and typical payment patterns. Deposits you’re expecting. Recurring revenue if you have any. Be realistic about timing. If your customers typically pay 45 days late, don’t assume they’ll suddenly pay on time.

List every expected outflow. Payroll is usually the biggest and most predictable. Rent, utilities, loan payments, insurance premiums. Recurring subscriptions. Then estimate variable expenses like materials, subcontractors, and supplies based on what you know about upcoming work.

Build a simple spreadsheet. Week 1 at the top, starting cash, plus inflows, minus outflows, equals ending cash. That ending cash becomes the starting cash for Week 2. Repeat for 13 weeks. The week where your ending balance goes negative or uncomfortably low is when you have a problem.

The 13-week window matters because it’s long enough to see problems coming but short enough that your estimates are still somewhat reliable. Beyond 13 weeks, you’re basically guessing. This kind of cash flow planning takes discipline but pays off when you spot trouble before it arrives.

Update the forecast weekly. Every Monday, delete last week, add a new week 13, and update your projections based on what actually happened and what you now know. A forecast that sits untouched for a month is useless.

For seasonal businesses like landscaping or construction in MetroWest, build in what you know about slow periods. If January through March is historically dead, your forecast needs to show that reality. Planning to collect the same revenue in February that you do in July is how people run out of cash in March.

Pay attention to timing mismatches. Contractors often have a gap between when they pay for materials and labor versus when they get paid by the customer. You might book a profitable job and still run out of cash because you’re floating expenses for 60 days before the check arrives. The forecast shows you this.

Watch committed costs, not just paid costs. You signed a contract with a sub for $15,000. You’ve paid $5,000 so far. That remaining $10,000 is coming whether you like it or not. Include it in your outflows even if you haven’t cut the check yet.

If the forecast shows a cash crunch coming, you have time to act. Speed up collections on overdue invoices. Delay vendor payments where you can without damaging relationships. Line up a credit line before you need it. Talk to your bank about options. The whole point is knowing early enough to do something about it.

Most small business owners don’t run out of cash because they’re unprofitable. They run out because they didn’t see the timing problem coming. A rolling forecast shows you the problem while there’s still time to fix it. Good bookkeeping services in MetroWest can help you build and maintain this kind of forecast so you’re not flying blind.