A cash flow forecast shows you whether you’ll have money in the bank when you need it, not just whether the business is profitable on paper. Before any large purchase, you need to see how that expense fits with all your other cash obligations over the coming weeks and months.

The forecast should start with your expected receipts. This means money you’re confident will come in based on invoices outstanding, contracts in place, or typical sales patterns. Don’t count revenue you hope for. Count revenue you can reasonably expect based on history and commitments.

Then layer in your recurring cash obligations. Payroll is usually the biggest and most inflexible. You can negotiate with vendors, but you can’t negotiate with employees. Add vendor bills that are due or coming due, focusing on the ones with real consequences for late payment. Include any loan payments or equipment financing you’re already committed to. Don’t forget estimated tax payments if you’re on a quarterly schedule.

Owner draws belong in this forecast too. If you’re taking regular draws for living expenses, those are as fixed as payroll from a cash perspective. Same with any inventory or materials purchases you’ll need to make to keep operations running. If your books are behind or messy, bookkeeping cleanup and catch-up services should come first so you have accurate historical data to project from.

Now add the large purchase you’re considering. Does your projected cash balance stay positive throughout the forecast period? Not just on the day of the purchase, but in the weeks after when other obligations come due? A $30,000 equipment purchase might look fine today, but if payroll is due next week and your biggest customer typically pays 45 days late, you could hit a wall.

Look at least 90 days out, longer if your business has seasonal patterns. A contractor buying a new truck in February needs to see what happens through slow spring months before summer projects bring cash back in. A retailer considering a large inventory buy in September needs to see past the holiday season to know if the cash will actually be there.

The forecast also tells you whether financing makes more sense than paying cash. Maybe you can afford the purchase outright, but doing so leaves no cushion for unexpected expenses. Financing the purchase and keeping cash reserves might be the smarter move even if it costs more in interest.

Building a proper cash flow forecast requires discipline but can prevent the kind of cash crunch that puts otherwise healthy businesses in trouble. The goal is to know before you commit whether this purchase fits your actual cash reality, not just your bank balance today.