Cash Flow Forecast: Build a 13-Week Forecast You'll Actually Update
Updated
A cash flow forecast estimates the money available at the end of each future week by adding expected receipts and subtracting scheduled payments. Start with usable cash, not money already committed elsewhere. Keep weeks across the top and payment categories down the side so collection delays and shortfalls are visible.
Closing cash = opening cash + receipts − payments
Next week opening cash = previous week closing cash
Key takeaways
Closing cash = opening cash + receipts − payroll − rent − supplies
Next week opening = previous week closing
Week 13 = $25,000 + 13 × ($12,000 − $8,500) − 4 × $6,000 = $46,500
Building a Cash Flow Forecast You Can Actually Use
A cash flow forecast answers a narrower, more concrete question than most financial statements: how much cash will actually be available, and when. Done well, it is a recurring, lightweight calculation you update regularly — not a one-time, highly detailed projection exercise that tries to predict every line item for the next several years.
Start With Usable Cash
Usable cash = bank balance + deposits in transit − checks/payments already issued but not yet cleared ± other reconciling items.
The starting point of any useful forecast is not the balance shown in your accounting software or even the raw bank balance — it's usable cash. That means taking your actual bank balance and then:
- Deducting checks, transfers, or payments that have already been issued but have not yet cleared the bank, and adding deposits in transit.
- Deducting payments already sent at your cutoff that the bank hasn't settled yet, such as a payroll run that has been processed but not yet settled. Payments scheduled for later, like an authorized vendor payment or a future ACH, are not subtracted here; schedule each one once, in the week it leaves.
- Confirming the remaining balance actually belongs to the business and isn't, for example, holding client trust funds or sales tax collected on behalf of a state that is not truly available for operating use.
Only after this reconciliation do you have a true "available cash" starting figure. Skipping this step can overstate your starting cash, because a bank balance may include checks that haven't cleared. Don't subtract an obligation at the start and again in a later week.
Keep the Forecast Simple and Recurring
A cash flow forecast works best as a recurring calculator you update on a set cadence (weekly for tight-cash businesses, monthly for more stable ones) rather than a single, highly detailed multi-year model. The reason is practical: the further out you project, and the more granular you try to get, the less accurate the forecast becomes, while the maintenance burden grows. A simple, consistently updated forecast that you trust and actually look at beats an elaborate one that goes stale after the first month.
A workable recurring structure looks like this:
- Starting cash (usable cash as defined above)
- Plus: expected cash inflows for the period (collections from customers, expected loan draws, owner contributions)
- Minus: expected cash outflows for the period (payroll, rent, loan payments, vendor payments, tax payments)
- Equals: projected ending cash
That projected ending cash becomes next period's starting point, and you repeat the cycle. Over time, you refine your inflow and outflow estimates based on how accurate previous periods turned out to be — but the structure itself stays simple.
Examples use made-up numbers. Education only, not tax, legal or investment advice.
Example: all 13 weeks
The setup
Thirteen weeks is roughly one calendar quarter.
It's far enough out to see a payroll crunch or a quarterly tax payment coming, and close enough to update and test assumptions weekly.
This is a separate, simpler business from the reconciliation example below.
The complete forecast table below starts with $25,000 available cash.
Services income is $12,000, payroll $7,000 and supplies $1,500 every week; rent is $6,000 only in weeks 1, 5, 9 and 13 (a simplified every-four-weeks schedule, not calendar-month rent).
Week 1 closes at $22,500; week 13 closes at $46,500.
Replace these example receipts and payments with your expected payment dates and amounts.
The 13-week window is a planning assumption, not a legal rule or external statistic.
| Line item | W1 | W2 | W3 | W4 | W5 | W6 | W7 | W8 | W9 | W10 | W11 | W12 | W13 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Opening cash | $25,000.00 | $22,500.00 | $26,000.00 | $29,500.00 | $33,000.00 | $30,500.00 | $34,000.00 | $37,500.00 | $41,000.00 | $38,500.00 | $42,000.00 | $45,500.00 | $49,000.00 |
| +Services income | $12,000.00 | $12,000.00 | $12,000.00 | $12,000.00 | $12,000.00 | $12,000.00 | $12,000.00 | $12,000.00 | $12,000.00 | $12,000.00 | $12,000.00 | $12,000.00 | $12,000.00 |
| −Payroll | $7,000.00 | $7,000.00 | $7,000.00 | $7,000.00 | $7,000.00 | $7,000.00 | $7,000.00 | $7,000.00 | $7,000.00 | $7,000.00 | $7,000.00 | $7,000.00 | $7,000.00 |
| −Rent | $6,000.00 | $0.00 | $0.00 | $0.00 | $6,000.00 | $0.00 | $0.00 | $0.00 | $6,000.00 | $0.00 | $0.00 | $0.00 | $6,000.00 |
| −Supplies | $1,500.00 | $1,500.00 | $1,500.00 | $1,500.00 | $1,500.00 | $1,500.00 | $1,500.00 | $1,500.00 | $1,500.00 | $1,500.00 | $1,500.00 | $1,500.00 | $1,500.00 |
| =Closing cash | $22,500.00 | $26,000.00 | $29,500.00 | $33,000.00 | $30,500.00 | $34,000.00 | $37,500.00 | $41,000.00 | $38,500.00 | $42,000.00 | $45,500.00 | $49,000.00 | $46,500.00 |
What Belongs in Inflows and Outflows
Inflows should reflect cash you reasonably expect to receive in the period, not revenue you've invoiced or booked. If a customer typically pays 30 days after invoice, a sale made this week shows up as a cash inflow next month, not this week.
Outflows should include every committed or highly predictable cash obligation: payroll (including payroll taxes), rent, loan principal and interest, recurring vendor payments, and tax payments (sales tax, estimated income tax, payroll tax deposits). Irregular but known outflows — an insurance premium due quarterly, a loan balloon payment — should be scheduled into the specific period they'll hit, not spread evenly across the year, since that would misstate cash availability in the actual month they occur.
A Worked Example (Assumptions Labeled)
The setup
Assume a business reconciles its bank balance as follows:
| Item | Amount |
|---|---|
| Bank balance (as shown) | $62,000 |
| Less: checks issued, not yet cleared | ($8,500) |
| Less: payroll processed, not yet settled | ($14,000) |
| usable cash | $39,500 |
From that $39,500 starting point, assume the business forecasts the next 30 days:
| Item | Amount |
|---|---|
| Starting available cash | $39,500 |
| Plus: expected customer collections | $45,000 |
| Minus: payroll (two future cycles, not including the run already deducted above) | ($28,000) |
| Minus: rent | ($6,000) |
| Minus: loan payment | ($3,200) |
| Minus: recurring vendor payments | ($9,500) |
| Projected ending cash | $37,800 |
Updating the Forecast
At the end of each period, compare your projected ending cash to what actually happened. Large variances are worth investigating: did a customer pay later than expected, did an unplanned expense come up, or was an estimate simply off? Over a few cycles, this comparison sharpens your inflow and outflow assumptions and makes the recurring forecast more reliable, without requiring you to build a more complex model.
Why This Beats a Detailed Long-Range Projection
A highly detailed, long-range cash projection can feel more rigorous, but it often creates false precision — specific numbers many months out that are really just guesses dressed up as forecasts. A simple, reconciled, recurring forecast focused on the near term gives you an honest, actionable picture of what's actually available, which is the entire point of doing this in the first place.
Common Reconciliation Pitfalls
Businesses using multiple bank accounts, merchant processors with delayed settlement, or lines of credit sometimes end up double-counting or missing cash in their starting balance. A merchant processor holding a day or two of card sales before depositing them, for example, is not yet available cash even though it will likely arrive soon — it should be reflected as an expected near-term inflow, not as part of today's usable cash. Being precise about what counts as "available right now" versus "expected to arrive shortly" keeps the forecast honest.
Make it a 15-minute weekly habit
Because this is meant to be a recurring calculator rather than a one-time model, build it in a format you'll actually maintain — a simple spreadsheet or lightweight tool that takes only a few minutes to update each period. The value of a cash flow forecast comes almost entirely from the discipline of updating it consistently and reconciling it against actual results, not from the sophistication of the underlying model.
Related lessons
Open the free 13-week cash flow template.
Five steps to a weekly forecast
- Start from usable cash: take your bank balance, then subtract payments already committed but not yet cleared and any money set aside for taxes or payroll.
- List expected receipts by week using the date customers are likely to pay, not the invoice date.
- List expected payments by week: payroll, supplier bills, rent, loan payments, taxes, owner draws.
- Ending cash = starting cash + receipts − payments; each week's ending cash is the next week's start.
- Update weekly: replace last week's guesses with what happened and add a new week so you always look 13 weeks ahead.
Illustrative example: four weeks
Examples use made-up numbers. Education only, not tax, legal or investment advice.
| Line item | Week 1 | Week 2 | Week 3 | Week 4 |
|---|---|---|---|---|
| Starting cash | $25,000.00 | $26,500.00 | $23,300.00 | $28,500.00 |
| Receipts | $18,000.00 | $14,000.00 | $21,000.00 | $12,000.00 |
| Payments | $16,500.00 | $17,200.00 | $15,800.00 | $19,400.00 |
| Ending cash | $26,500.00 | $23,300.00 | $28,500.00 | $21,100.00 |
Weeks 2 and 4 dip because payments land before receipts; the forecast shows it early.
Why 13 weeks
It is one quarter, long enough to catch tax dates, payroll cycles and slow-paying customers, and short enough to forecast with real dates.
Get the worksheet
A printable template with a blank 13-week cash grid. Open it now or have the link emailed to you.
The Owner Track Letter
One cash decision. One AI workflow.
Questions owners ask
Should I start a forecast from my bank balance?
Start from usable cash — your bank balance reconciled for deposits in transit and payments already issued but not yet cleared — not the raw balance. Then schedule each future payment once, in the week it leaves.
How detailed should the forecast be?
Keep it as a simple, recurring calculator you update regularly rather than a highly detailed, long-range projection.
How often should I update it?
A common cadence is weekly for tight-cash businesses and monthly for more stable ones; update on whatever consistent schedule you'll actually maintain.
Are merchant processor funds part of available cash?
Only once settled into your bank account. Pending settlements should be treated as an expected near-term inflow, not current available cash.
Why 13 weeks?
It's roughly one quarter: long enough to catch lumpy payments like quarterly taxes or insurance, short enough that your estimates stay realistic.
How accurate does it need to be?
Accurate enough to see the dips and the timing; update it weekly.
Cash flow vs profit?
Profit is revenue minus costs; cash is the timing of money in and out.
What if I do not know when customers will pay?
Use your average days to pay from past invoices and be conservative.
Sources
Connect the numbers
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