# Average debtors collection period formula: worked example

> The average debtors collection period formula, three variants side by side, and a worked example showing why one company can get 58, 50 or 49 days.

Canonical: https://www.invoqk.com/blog/average-debtors-collection-period-formula-worked-example
Last updated: 2026-11-04

## Key takeaways

- Average collection period equals average receivables divided by net credit sales, multiplied by the days in the period.
- One company can show 58.3, 50.0 or 49.3 days depending on whether closing or average receivables and a 365 or 360 day year are used.
- Cash sales must be excluded, and in the UK and Germany tax must be matched on both sides, or the result is wrong by 10 days or more.

The **average collection period** is the average number of days a business takes to turn a credit sale into cash. It is also called the debtors collection period or receivables days. A lower number means customers pay sooner and cash arrives faster.

In short: divide your receivables by your credit sales, then multiply by the number of days in the period. Which receivables figure you use, and which sales figure, changes the answer by ten days or more.

This guide gives the formula, shows the three common variants side by side on one company, and explains the UK VAT trap that inflates the result. It also lists what to do when the number is too high.

![One company, four answers: days to collect](https://www.invoqk.com/charts/average-debtors-collection-period-formula-worked-example-variants.svg)

## What is the average debtors collection period formula?

The average debtors collection period formula divides average trade receivables by credit sales for the period, then multiplies the result by the number of days in that period. **Trade receivables** are also called debtors or accounts receivable. They are the amounts customers owe you for invoices you have issued but not been paid.

The formula is:

**Average collection period = (average receivables ÷ net credit sales) × days in the period**

Average receivables is the opening balance plus the closing balance, divided by two. Net credit sales are sales made on credit terms, minus returns and discounts. Use 365 days for a year, or the real number of days for a month or quarter.

Three other names point to the same idea: days sales outstanding (DSO), receivable days and debtor days. DSO is the usual name in the USA, and debtor days is the usual name in the UK. Most textbooks treat them as the same calculation, though some DSO formulas use closing receivables only.

## How do you calculate the average collection period step by step?

You calculate it in five steps: pick the period, find the receivables, find the credit sales, divide, then multiply by the days. Follow the steps in order.

1. **Pick the period.** Use a full year, a quarter or a month. Do not mix periods.
2. **Find opening and closing receivables.** Read them from the balance sheet or your accounts receivable ageing report.
3. **Average them.** Add opening and closing receivables and divide by two.
4. **Find net credit sales.** Take total sales on credit terms. Leave out cash sales, because a cash sale never creates a receivable.
5. **Divide, then multiply by the days.** Receivables ÷ credit sales × 365 gives the days.

Invoqk's [DSO calculator](/dso-calculator) runs these steps from two inputs if you want a quick check.

## What does a worked example look like?

A worked example uses one company and one year. Here is a small supplier with these figures, all in US dollars.

| Item | Amount |
|---|---|
| Net credit sales for the year | $1,000,000 |
| Cash sales for the year | $187,000 |
| Receivables at start of year (opening) | $114,200 |
| Receivables at end of year (closing) | $159,800 |

Apply the formula to the average:

1. Average receivables = ($114,200 + $159,800) ÷ 2 = $137,000.
2. Receivables ÷ credit sales = $137,000 ÷ $1,000,000 = 0.137.
3. Days = 0.137 × 365 = **50.0 days**.

On average, this company waits 50 days after invoicing to be paid. If its terms say Net 30, customers are paying about 20 days late on average.

## Which of the three formula variants should you use?

Use the average-receivables variant for annual reporting, the closing-receivables variant for a quick check, and the period variant for monthly tracking. Each gives a different answer on the same data, and the table shows when each one fits.

| Variant | Formula | Use when |
|---|---|---|
| Closing | Closing receivables ÷ credit sales × days | A quick check |
| Average | Average receivables ÷ credit sales × days | Annual reports |
| Period | Receivables ÷ period credit sales × days in the period | Monthly tracking |

![Three formula variants for average collection period](https://www.invoqk.com/charts/average-debtors-collection-period-formula-worked-example-formulas.svg)

The closing variant is faster but distorts the answer when sales are growing, because closing receivables are large compared with the year's earlier sales. The average variant smooths this out. The period variant matters when sales are seasonal, since an annual average hides a bad quarter.

## Why can the same company get four different answers?

The same company gets different answers because each variant uses a different receivables figure or sales base. This is the part most guides skip, so the comparison below runs all four on the figures above.

| Method | Calculation | Result |
|---|---|---|
| Closing receivables | $159,800 ÷ $1,000,000 × 365 | 58.3 days |
| Average receivables | $137,000 ÷ $1,000,000 × 365 | 50.0 days |
| Average, 360-day year | $137,000 ÷ $1,000,000 × 360 | 49.3 days |
| Wrong: cash sales included | $137,000 ÷ $1,187,000 × 365 | 42.1 days |

The first three are legitimate and differ only by method. The fourth is an error. Putting cash sales in the denominator makes customers look faster, because the cash sales never produced a receivable. The company would appear to collect in 42 days when real credit customers take 50.

State the method whenever you quote the number. Comparing a closing-balance figure from one company with an average-balance figure from another is meaningless.

## Why does VAT make the UK figure wrong?

In the UK, debtors include VAT but sales are usually recorded net of VAT, so dividing one by the other overstates the days. Receivables are what customers owe, and that includes VAT at 20%, according to [HMRC's standard rate](https://www.gov.uk/vat-rates). Sales on the income statement exclude it.

Take a UK business with debtors of £260,000 that include VAT. Net credit sales are £1,000,000, or £1,200,000 once 20% VAT is added.

| Denominator | Calculation | Days |
|---|---|---|
| Net sales (wrong) | £260,000 ÷ £1,000,000 × 365 | 94.9 |
| VAT-inclusive sales | £260,000 ÷ £1,200,000 × 365 | 79.1 |

The like-for-like figure is 79.1 days. Using net sales makes the business look 16 days slower than it is. Match the two sides: either remove VAT from the debtors or add it to the sales.

![UK trap: VAT in debtors but not in sales](https://www.invoqk.com/charts/average-debtors-collection-period-formula-worked-example-uk-vat.svg)

The same mismatch occurs in Germany with Umsatzsteuer at 19% and in any US state where sales tax is billed on invoices and recorded as a liability rather than as sales. If your receivables include tax, include tax in the sales figure too.

## What is a good average collection period?

A good average collection period is close to your payment terms, usually within about 10 days of them. If you invoice on Net 30 terms, an average of 35 days is healthy and an average of 60 days means customers are routinely late.

Compare yourself with your own terms, not with another industry. The meaning of the number comes from the gap.

| Your terms | Average collection period | Reading |
|---|---|---|
| Net 30 | 31-40 days | Healthy |
| Net 30 | 41-55 days | Slipping; chase earlier |
| Net 30 | 56+ days | Collections problem |
| Net 60 | 61-70 days | Healthy |

These bands are a rule of thumb for reading your own result, not an official benchmark. Trade credit norms differ by sector and country.

Check each customer's due date with the [invoice due date calculator](/invoice-due-date-calculator). A rising trend matters more than any one reading. If the figure moves from 38 to 46 to 54 over three quarters, customers are paying later even if the latest number looks tolerable.

## How is the average collection period different from receivables turnover?

**Receivables turnover** is the number of times a year you collect your average receivables. It counts how many times a year you collect your average receivables, while the collection period expresses the same fact in days. They are inverses. Dividing 365 by the turnover ratio gives the collection period.

In the worked example, turnover is $1,000,000 ÷ $137,000 = 7.3 times a year. Then 365 ÷ 7.3 = 50.0 days. Use whichever reads better for your audience: finance teams often quote turnover, while owners find days easier to act on.

## How do you track the collection period every month?

You track it monthly with the period variant: that month's receivables divided by that month's credit sales, multiplied by the days in the month. For example, a business with $150,000 of receivables at the end of June and $90,000 of June credit sales has a June figure of $150,000 ÷ $90,000 × 30 = 50.0 days.

Plot the monthly figure on a simple chart and look at the direction. A seasonal business should compare June with last June, not with December. Record the method in the same spreadsheet so that every month is calculated the same way, and so that a colleague can repeat the calculation without asking you.

## What does a high collection period cost you?

A high collection period ties up cash that you have already earned. Every extra day of delay on $1,000,000 of annual credit sales leaves about $2,740 more owed to you at any moment ($1,000,000 ÷ 365).

At 50 days, the company in the example is financing roughly $137,000 of customer purchases. Cutting the figure to 40 days would release about $27,400 of cash (10 days × $2,740). That is cash you can use without borrowing.

Late payment also carries a legal cost for the customer, and the [late fee calculator](/late-fee-calculator) shows the amount. In the UK, statutory interest on a late commercial debt is 8% plus the Bank of England base rate, according to [GOV.UK guidance on charging interest on a commercial debt](https://www.gov.uk/late-commercial-payments-interest-debt-recovery/charging-interest-commercial-debt). German law sets 9 percentage points above the base rate for business-to-business claims and a €40 flat fee, according to [BGB section 288](https://www.gesetze-im-internet.de/bgb/__288.html).

## How do you reduce your average collection period?

You reduce it by invoicing sooner, shortening terms, chasing earlier and making payment easy. Work through these in order of cost, cheapest first.

1. **Invoice the day the work is done.** Every day you wait to send the invoice adds a day to the figure.
2. **Shorten the terms.** Moving from Net 45 to Net 30 removes about 15 days if customers follow terms.
3. **Ask for a deposit.** A [deposit invoice](/templates) brings cash in before the work starts and reduces the balance outstanding.
4. **Send reminders on a schedule.** A reminder a few days before the due date works better than a chase after it.
5. **Offer easy payment methods.** A payment link or bank details with a reference remove excuses.
6. **Review the oldest invoices weekly.** Use an ageing report and call the largest overdue balances first.

Invoqk's [payment reminder email generator](/payment-reminder-email-generator) writes the wording for the reminder step.

## Common mistakes when you calculate the average collection period

Most wrong answers come from mismatched inputs, not from the formula. Check these before you trust a number.

| Mistake | Effect | Fix |
|---|---|---|
| Cash sales in the denominator | Days look too low | Use credit sales only |
| VAT or sales tax in debtors only | Days look too high | Match both sides |
| Mixing a year-end balance with monthly sales | Wrong scale | Use the same period |
| Using 365 for a 90-day quarter | Wrong multiplier | Use the real days |
| Ignoring bad debts | Days look better than reality | Show them separately |

Write down the method you chose and keep it the same each time. A consistent method makes the trend reliable even if the exact figure is debatable.

## Key points

The average collection period is average receivables ÷ net credit sales × days. Use credit sales only, match tax treatment on both sides, state which receivables figure you used and compare the result to your payment terms.

## FAQ

### What is the formula for the average debtors collection period?

Average debtors collection period = average trade receivables ÷ net credit sales × days in the period. Average receivables is opening plus closing receivables divided by two. Use 365 for a year, or the real number of days for a month or a quarter, and use credit sales only.

### Is the average collection period the same as DSO?

Mostly yes. Days sales outstanding, debtor days and receivable days describe the same idea. Some DSO formulas use closing receivables rather than the average, so state which one you used whenever you quote the figure, and never compare two companies that used different methods.

### How do you calculate the average collection period for a month?

Divide that month's receivables by that month's credit sales and multiply by the days in the month, such as 30 or 31. Use the same month on both sides, never an annual sales figure. For June, that is June receivables over June credit sales times 30.

### What counts as a good collection period?

A good result is close to your payment terms, usually within about 10 days. On Net 30 terms, 31-40 days is healthy. A figure that rises each quarter is a warning even if it still looks acceptable, so track the trend and not only the latest value.

### Should cash sales be included in the calculation?

No. Cash sales never create a receivable, so including them in the denominator makes customers appear to pay faster than they do. Use net credit sales only, minus returns and discounts, and compare receivables with sales on the same tax basis.

## Related

- [Free invoice template guides: compliance & getting paid](https://www.invoqk.com/blog)
- [Invoqk home](https://www.invoqk.com)