Direct answer: An ecommerce cash flow forecast projects opening cash, monthly inflows (payouts after returns and processing delays), and outflows (COGS, ads, fixed costs, inventory buys) to show your month-end bank balance.
This guide walks through a 90-day template and includes a free calculator that renders month-by-month cash without a spreadsheet.
Who this is for
US ecommerce owners who buy inventory, run paid ads, and want a simple 3-month bank-balance projection before making capital decisions.
Structure of the forecast
- Opening cash: bank balance today.
- Inflows: payouts from Shopify/Amazon/Stripe minus refunds, adjusted for payout delay.
- COGS / inventory buys: month-by-month PO commitments.
- Ad spend: scheduled Meta, Google, TikTok, Amazon Ads spend.
- Fixed costs: rent, salaries, software, insurance.
- Ending cash: opening + inflows − outflows.
Illustrative 3-month forecast
| Line | Month 1 | Month 2 | Month 3 |
|---|---|---|---|
| Opening cash | $20,000 | $18,600 | $8,700 |
| Payouts (net) | $26,000 | $26,000 | $28,000 |
| Ad spend | $10,800 | $10,800 | $11,500 |
| Inventory buy | $8,600 | $15,000 | $8,600 |
| Fixed costs | $8,000 | $8,000 | $8,000 |
| Ending cash | $18,600 | $8,700 | $8,600 |
Example calculation (USD)
Store forecasts $60k monthly revenue, 40% COGS, 18% ad spend, 8% return rate, 14-day average payout delay, and $8k fixed costs. With a $15k inventory buy in Month 2, cash tightens from $20k to $8,700 by end of Month 2 — a signal to delay the buy or negotiate 30-day terms with the supplier.
Common mistakes to avoid
- Recording gross sales as cash — payouts arrive later and net of fees.
- Ignoring refund lag — returns often hit the bank a week after issue.
- Forgetting quarterly bills like sales tax and payroll taxes.
- Modeling only best-case revenue with no downside scenario.
Best practices
- Reconcile forecast vs actual weekly for the first quarter.
- Add a 15% buffer to Q4 ad spend forecasts.
- Model both a base and a stress scenario.
Frequently asked questions
Do I need accounting software for this?
No — a spreadsheet works. Software helps once you cross ~$50k/month in revenue.
How far out should I forecast?
90 days is the sweet spot for most small stores. Quarterly refresh.