Cash flow calculator
Your cash month by month, side by side: if customers paid on time, and as they actually pay. See how much late payment is holding up, and whether it runs your balance below zero.
No account, no email wall. It runs entirely in your browser — nothing you type leaves it.
Held up by late payment
$16,800
Money you have invoiced that is still with customers at the end of the forecast, compared with everyone paying on time.
Cash runs out in
Month 1
With customers paying as late as you said.
At 21 days late, you run out of cash in month 1, even though on paper you invoice $24,000 a month. Late payment, not the business, is what empties the account.
| Month | Cash in (on time) | Balance (on time) | Cash in (late) | Balance (late) |
|---|---|---|---|---|
| 1 | $24,000 | $16,500 | $7,200 | -$300 |
| 2 | $24,000 | $18,000 | $24,000 | $1,200 |
| 3 | $24,000 | $19,500 | $24,000 | $2,700 |
| 4 | $24,000 | $21,000 | $24,000 | $4,200 |
| 5 | $24,000 | $22,500 | $24,000 | $5,700 |
| 6 | $24,000 | $24,000 | $24,000 | $7,200 |
A forecast, not accounting advice
It assumes the same invoicing, outgoings and delay every month, and that no invoices from before the forecast are still being paid. Real months vary. Use it to see the size of the effect, and see an accountant for a forecast you will borrow against. To see which invoices are holding up your cash right now, use the invoice aging calculator; for what the delay costs you in money, the late payment calculator.
Questions about cash flow and late payment
- How do I calculate cash flow for a small business?
- Start with the cash you have, add what actually comes in each month, and subtract what goes out. The catch is "actually": what you invoice in a month is not what you collect in it if customers pay late. This calculator runs both versions side by side so you can see the difference.
- How does this model late payment?
- It takes your average days late and assumes that share of each month's invoicing arrives a month later: 21 days late means 21/30 of a month's invoicing lands the following month. 45 days late means everything arrives at least a month late and half of it two months late. It is a plain approximation, the same every month, so you can see the effect of one number.
- Why can I run out of cash when I'm profitable?
- Because profit counts what you have earned and cash counts what you have been paid. If you invoice more than you spend but customers pay weeks late, the gap is funded from your bank balance until they do. Early in a business, or after a growth spurt, that gap is often larger than the cash you have.
- What does "held up by late payment" mean?
- The difference between your bank balance at the end of the forecast if everyone paid on time and if they paid as late as you said. It is money you have earned that is sitting with your customers.
- Is my data stored anywhere?
- No. There is no signup and no server call; it all runs in your browser.
Collectly does this across every invoice, on its own
You just forecast your cash. Collectly does the same thing continuously for every unpaid invoice you have — reads the replies, works out why each one is unpaid, estimates when it will land, and drafts the follow-up for you to approve.
With 15 rules it cannot talk its way around
- A paid or written-off invoice is never chased again. Follow-ups are switched off permanently, not deferred.
- A disputed invoice stops automated chasing entirely and goes to a person to resolve.
- A promise to pay on a date pauses reminders until that date has passed. Collectly checks back the day after, not on the day.
- At least three days between reminders on the same invoice, so re-running the analysis cannot turn into nagging. A resent or corrected invoice the customer has just asked for is not a reminder, and still waits for your approval.
Want customers to pay closer to on time?
Two things, both free, both opt-in. You confirm by email before anything is sent.
More free tools on the tools index.