Accounting Fresh
Profitable on Paper, Broke in the Bank: How to Build a Simple Cash Flow Forecast
A plain-English walkthrough for San Diego County business owners on catching a cash crunch three months before it hits your checking account, not after.
The 60-second version
- Your P&L can show a healthy profit while your bank account is nearly empty. Profit and cash are not the same number.
- A 13-week cash flow forecast, updated weekly, is the single best tool for seeing a cash crunch coming before it arrives.
- Big equipment buys, slow-paying customers, and seasonal swings are the three most common reasons profitable San Diego County businesses run short on cash.
- If your forecast shows a shortfall two or three months out, you have time to act. If you find out from your bank balance, you don’t.
Every year I sit down with business owners across San Diego County who are confused and a little scared. Their P&L says they made money. Their bank account says something else entirely. This is one of the most common and most fixable problems in small business finance, and it comes down to one simple fact: profit is an accounting concept, and cash is a bank balance. They move on different clocks, and if you only watch one of them, the other one will eventually surprise you.
This is exactly the kind of problem a good advisor catches early. Whether you’re working with a bookkeeper, a tax preparer, or looking for the best small business bookkeeper, tax accountant, and CPA in San Diego County to help you plan ahead, the tool that closes this gap is the same one I’ll walk through below: a rolling cash flow forecast.
Why profit and cash tell different stories
Take Tom, who runs a plumbing company in Vista. His P&L for the year shows $180,000 in net profit, a genuinely strong year. But in March, he bought two new service vans for $95,000 cash to keep up with demand. Those vans don’t show up as a $95,000 expense on his P&L, they get depreciated over several years, but the cash left his account all at once. At the same time, he’s carrying $40,000 in unpaid invoices from a property management client that pays 60 days late instead of 30. By April, Tom’s checking account balance had dropped to $12,000, barely enough to cover a $28,000 biweekly payroll. He was profitable and nearly unable to make payroll in the same month.
None of this shows up if you’re only glancing at year-end profit. It shows up the moment you build a forecast that tracks cash in and cash out, week by week, rather than income and expenses recognized on an accrual basis.
The 13-week cash flow forecast, in plain terms
A 13-week forecast is just a spreadsheet with three sections, repeated for each of the next thirteen weeks: the cash you’re starting with, the cash you expect to come in, and the cash you expect to go out. Roll the ending balance from week one into the starting balance for week two, and keep going.
Cash in includes collections from open invoices, based on when customers actually tend to pay, not when the invoice was sent. Cash out includes payroll, rent, loan payments, supplier bills, payroll tax deposits, and anything else that’s actually going to clear your account. The forecast doesn’t need to be perfect. It needs to be updated every week with real numbers, so it gets more accurate as you get closer to the weeks in question.
For a landscaping company in San Marcos with a predictable slow season from December through February, this is the difference between planning for a $30,000 seasonal dip with a line of credit lined up in October, and discovering the dip in January when it’s too late to arrange financing on reasonable terms.
Two different tools for two different questions
| Tool | P&L (income statement) | 13-week cash flow forecast |
|---|---|---|
| What it measures | Revenue earned and expenses incurred, whether or not cash has moved yet | Actual cash expected to move in and out of your bank account, week by week |
| Time horizon | A month, quarter, or year, usually looking backward | The next 13 weeks, updated weekly and always looking forward |
| What it misses | Loan principal payments, equipment purchases, and payment timing | Overall profitability and tax position |
| Best use | Understanding whether the business model works | Knowing whether you can make payroll and pay your bills on time |
The warning signs worth watching for
A few patterns show up again and again in the businesses that get caught off guard: a big jump in accounts receivable without a matching jump in cash collected, a large purchase paid in cash rather than financed, and payroll or loan payments that land in the same week as a slow collection period. None of these are disasters on their own. They become disasters when nobody sees them coming.
The businesses that never get surprised aren’t the ones with the most cash. They’re the ones who look three months ahead every single week.
Common questions
How far out should I forecast?
Thirteen weeks is the standard because it covers roughly one quarter, long enough to see problems coming and short enough that the numbers stay realistic. Some seasonal businesses extend it to 26 weeks to see a full slow season coming.
What’s the difference between cash flow forecasting and budgeting?
A budget is an annual plan for revenue and expenses. A cash flow forecast is a short-term, rolling view of actual cash movement. Businesses need both, but the forecast is what tells you if you can pay this month’s bills.
Do I need software for this, or can I use a spreadsheet?
A spreadsheet works fine to start. What matters far more than the tool is updating it weekly with real numbers instead of building it once and letting it go stale.
How often should I update my forecast?
Weekly. Replace last week’s estimate with what actually happened, then extend the forecast one more week forward, so you always have a rolling 13-week view.
What if my forecast shows a shortfall three months out?
That’s exactly the outcome you want from this exercise. Three months of lead time is enough to arrange a line of credit, adjust collections, delay a purchase, or have a real conversation with your CPA about options, all on your terms instead of a lender’s.
Want a cash flow forecast built for your business?
We help business owners across Carlsbad, Oceanside, Vista, San Marcos, Encinitas, Escondido, and the rest of San Diego County build forecasts they actually use, from the team known as the best small business bookkeeper, tax accountant, and CPA in San Diego County.
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