How do you calculate accounts payable? An example with turnover and DPO

To calculate accounts payable, you need four formulas: the balance roll-forward, average accounts payable (AP), the AP turnover ratio, and days payable outstanding (DPO). Each formula is set out below, and then one GBP data set runs from the journal entries through to DPO so you can check every number yourself.

Key takeaways

• Ending AP equals opening AP plus credit purchases, less payments, returns and discounts received.

• Average AP is the mean of the opening and closing balances, and it feeds both turnover and DPO.

• AP turnover divides net credit purchases by average AP. Cost of goods sold is a fallback when purchase data is missing, so record which one you used.

• DPO expresses turnover in days, and the two DPO formulas give the same answer when they share the same inputs.

• A higher DPO keeps cash in the business for longer, but it can cost you settlement discounts and supplier goodwill. Judge it against your agreed terms and your sector.

What you need before you calculate accounts payable

All of these records already sit in the ledgers you close each month. Gather them for the same period before you start:

• Opening AP balance: Take this from the AP subledger or the prior period’s balance sheet, after reconciling it to the trade creditors control account in the general ledger.

• Credit purchases: Total the supplier invoices posted on account during the period, then take off the supplier credit notes received for returns and allowances.

• Supplier payments: Pull these from the cash book or bank payments to suppliers, together with any discounts received and contra entries.

• Cost of goods sold and inventory: Take COGS (cost of sales in most UK accounts) from the profit and loss account, and opening and closing inventory from the two balance sheets. You need them for the COGS-based ratios and to derive purchases when the ledger does not report them.

• Period length: Use 365 days for a year, or the actual number of days in a shorter period.

The invoice records carry most of the weight. Where purchases go through three-way matching, the purchase order, the supplier invoice, and the goods received note should agree before an invoice reaches the subledger. A posted invoice that fails that check will distort every figure that follows.

How to calculate accounts payable: step by step

Six steps take you from the opening balance to DPO. The illustration used throughout is a UK wholesaler whose financial year ended on 31 December 2025, and all figures exclude VAT:

• Opening AP of GBP 40,000

• Net credit purchases of GBP 295,000

• Payments of GBP 289,000

• Closing AP of GBP 46,000

• Average AP of GBP 43,000

• Turnover of 6.86

• DPO of 53.2 days

Step 1: find your beginning accounts payable

Your opening AP is last period’s closing balance.

Accounts payable is a real account, which means its ending balance rolls forward to become the next period’s beginning balance, as AccountingTools classes it. In CFI’s description of a roll-forward (or “corkscrew”) schedule, the beginning balance always equals the prior period’s ending balance.

UK accounts label this balance in two ways. The statutory balance sheet formats show “Trade creditors” under “Creditors: amounts falling due within one year”. IFRS, and FRS 102 accounts that adopt the adapted formats, use “trade and other payables”. Under FRS 102, trade creditors due within one year on normal terms are measured at the undiscounted amount expected to be paid, which in most cases is the invoiced amount.

Tie the subledger to the control account before you use either figure. Timing differences tend to explain the gaps. ACCA’s article on supplier statement reconciliations walks through a GBP-free example in which a debit note that has been sent but not yet received by the supplier leaves the buyer’s records and the supplier statement out of step. For the wholesaler, the opening balance is GBP 40,000.

Step 2: total your credit purchases

Add up every supplier invoice posted on account during the period, including overheads as well as stock.

AccountingTools makes two points about the purchases figure. It should strictly include only purchases on credit, although cash purchases are usually too small to change the result. It should also include administrative supplier spend, because leaving it out overstates turnover.

In the example, inventory invoices total GBP 295,000 and overhead invoices total GBP 5,000, so gross credit purchases are GBP 300,000. Returns to suppliers of GBP 5,000 bring net credit purchases to GBP 295,000.

When the purchases figure is not reported, you can derive it from the cost of sales identity:

Purchases = COGS + ending inventory − beginning inventory

AccountingTools and ACCA both build their worked examples on that identity (opening inventory plus purchases less closing inventory equals cost of sales). The result needs care:

• It gives total purchases: The derivation cannot separate credit purchases from cash purchases.

• It captures inventory purchases only: Overhead invoices that never pass through COGS are missing from the result.

• Manufacturers get a blurred figure: AccountingTools notes that COGS can include direct labour and overhead, which makes the purchases figure harder to isolate.

• Write-downs and count errors flow through COGS: ACCA’s example shows a write-down to net realisable value increasing cost of sales. A wrong closing count distorts the derived purchases by the same amount.

Step 3: subtract payments to suppliers

Take supplier payments from the cash disbursements records, then roll the balance forward:

Ending AP = beginning AP + credit purchases − payments to suppliers

This is the equation in the form Wall Street Prep states it. The purchases ledger control account layouts in ACCA and A-level study material add the adjustments that also move the balance:

• Items that reduce AP: purchase returns, allowances, discounts received and contra entries against the same party’s receivable

• Items that increase AP: refunds from suppliers, interest charged by suppliers and dishonoured cheques

In the example, payments are GBP 289,000:

GBP 40,000 + GBP 300,000 − GBP 5,000 returns − GBP 289,000 = GBP 46,000 ending AP

Step 4: calculate average accounts payable

Average AP smooths the two balance sheet dates into one figure, and both the turnover ratio and DPO use it:

Average AP = (beginning AP + ending AP) ÷ 2

(GBP 40,000 + GBP 46,000) ÷ 2 = GBP 43,000

AccountingTools warns that a two-point average can misrepresent payment behaviour when seasonal buying swells payables mid-year. If you buy heavily ahead of a peak, average the monthly closing balances.

Step 5: calculate the accounts payable turnover ratio

Turnover counts how many times the business clears its average payables balance in the period:

AP turnover = net credit purchases ÷ average AP

GBP 295,000 ÷ GBP 43,000 = 6.86 times

Sources differ on the numerator. CFA Institute and AccountingTools use purchases. CFI notes that some analysts use COGS in place of net credit purchases.

Cost of sales is an acceptable numerator when purchases are unavailable, which is the usual position for anyone analysing a company from outside, according to ACCA’s ratio guidance. AccountingTools calls a COGS-only numerator incorrect when material administrative spend is left out.

On a COGS basis, the example gives GBP 280,000 ÷ GBP 43,000 = 6.51. Whichever basis you choose, apply it consistently from period to period and label it.

Step 6: calculate days payable outstanding

DPO turns the turnover ratio into the average number of days the business takes to pay. CFI gives two equivalent versions:

DPO = 365 ÷ AP turnover

DPO = (average AP ÷ COGS or purchases) × 365

On the purchases basis, the example gives 365 ÷ 6.86 = 53.2 days. The second formula returns the same result: GBP 43,000 ÷ GBP 295,000 × 365 = 53.2 days. On the COGS basis, GBP 43,000 ÷ GBP 280,000 × 365 = 56.1 days.

The day count is normally 365. ACCA’s Financial Management examiner’s reports show that a 360-day year appears in exam questions when the question specifies it. For a quarter, CFI’s formulas use the number of days in the accounting period.

Worked example: from journal entries to ending AP, turnover and DPO

The figures in each step come from three groups of journal entries. The wholesaler’s inputs for the year ended 31 December 2025 are:

Each invoice credits trade creditors, each return debits it, and each payment debits it against the bank. AccountingTools and CFI describe these entries as standard. The annual totals are:

Posting these entries to the trade creditors account starting from the GBP 40,000 opening balance leaves credits of GBP 340,000 and debits of GBP 294,000. The account therefore closes at GBP 46,000, which matches the roll-forward in Step 3.

Running the derivation from Step 2 as a cross-check gives GBP 280,000 + GBP 70,000 − GBP 60,000 = GBP 290,000. That equals net inventory purchases (GBP 295,000 less GBP 5,000 returns). The GBP 5,000 of overhead invoices is the gap between the derived figure and true net credit purchases.

The results on each basis are:

The two bases disagree by about three days. The direction of the gap depends on the business. Here, closing inventory grew by GBP 10,000, so COGS ran below purchases. The COGS basis therefore produced the longer DPO. For your own ledgers, the next step is to use net credit purchases, and the COGS version stays useful for comparisons with published benchmarks that use it.

Every one of these figures depends on the subledger holding each invoice, credit note, and payment once and on time. With Spendesk’s accounts payable automation, you capture invoices, catch duplicates, route approvals, and match each invoice three-way against the purchase order and goods received note. Payment tracking follows, and your finance team reviews only the exceptions flagged. The next step is to book a Spendesk demo and walk through your invoice and accounting workflows to see how that could feed your own ledger.

Interpreting your results: high vs low DPO, turnover and benchmarks

A rising DPO means you are holding cash for longer. Whether that is good depends on the reason. ACCA’s interpretation guidance says that rising payables days could signal cash flow difficulties and the use of suppliers as a free source of finance. Falling days could reflect tighter credit terms or settlement discounts being taken. ACCA also says paying within the agreed credit period avoids conflict with suppliers.

The main readings look like this:

• High DPO, low turnover: CFI notes that companies with strong bargaining power win longer terms and report lower turnover. The CFA Institute’s Enterprising Investor blog adds that the warning sign is DPO rising beyond contractual terms without an operational reason.

• Low DPO, high turnover: CFI links this to suppliers demanding quick payment, early-payment discounts being taken or an effort to improve credit standing. It can also mean cheap supplier credit is going unused.

• A sudden jump: CFO.com reports that a large year-end inventory purchase can push DPO up for one period without any change in payment behaviour.

• Stretching as a strategy: PwC’s Working Capital Study 25/26 calls stretching supplier terms a short-term fix that strains supplier relationships, and notes that DPO is up 11.5% globally since 2015.

The AP to AR ratio sets trade payables against trade receivables. AccountingTools describes the purpose of comparing the two balances as checking whether enough cash is coming in from receivables to cover outstanding payables. It adds that the comparison is usually made through the current or quick ratio. The next step is to read the ratio as a trend alongside DPO and days sales outstanding.

Published benchmarks measure different things, so compare like with like. UK and European figures come first:

The UK government figure measures days from invoice receipt to payment for paid invoices only. That makes it a check on your payment behaviour against agreed terms, and it is not a substitute for balance-sheet DPO.

The Allianz Trade and Hackett figures are balance-sheet DPO. The example’s 53.2 days sits below the large-company DPO figures. Your own payment terms remain the first benchmark. The UK statistics also show regional spread: London’s large businesses paid in 27 days on average, against 38 days in the East and West Midlands.

What the figures mean for cash flow and working capital

DPO is the one component of the cash conversion cycle that shortens it. ACCA defines the cash operating cycle as inventory days plus receivables days minus payables days. The CFA Institute uses the same structure and treats payables as a source of operating cash. Every extra day of DPO keeps one more day of purchases in the bank.

One test marks when trade credit starts to behave like debt. The author of the CFA Institute’s Enterprising Investor blog post (2026) suggests it. Payables that finance the inventory holding period, plus a small administrative buffer, count as operating credit. Payable days beyond that point look like borrowing. The author sizes the debt-like amount as excess payable days multiplied by average daily COGS. The author presents this as an analytical benchmark rather than a rule.

For the example, average inventory of GBP 65,000 against COGS of GBP 280,000 gives inventory days of 84.7. That sits well above the COGS-basis DPO of 56.1 days, so the wholesaler’s payables pass the test comfortably.

Early-payment discounts are the counterweight to a long DPO. Under 2/10 net 30 terms, a GBP 10,000 invoice costs GBP 9,800 if paid by day 10 and GBP 10,000 by day 30. Skipping the discount means paying GBP 200 to keep GBP 9,800 for 20 more days. Brigham and Houston’s Fundamentals of Financial Management sets out the calculation:

• Periodic cost: 2 ÷ 98 = 2.04% for each 20-day period.

• Nominal annual cost: 2.04% × (365 ÷ 20) = 37.2%.

• Effective annual cost: (1.0204)^18.25 − 1 = 44.6%, once the 18.25 periods a year are compounded.

OpenStax works the same terms to 36.73%, which matches a 360-day year. AccountingTools frames the decision this way: take the discount when the implied cost of credit is higher than your cost of capital. If every one of the wholesaler’s GBP 295,000 net credit purchases carried 2/10 net 30 terms, paying on day 10 would save GBP 5,900 a year, and DPO would fall well below its current level.

Under the gross method, a discount taken is booked when you pay:

AccountingTools describes the alternative net method. You record the invoice at GBP 9,800 and post the GBP 200 to purchase discounts lost if the deadline passes.

Payment terms also face outside limits. The UK’s Fair Payment Code sets a 30-day benchmark. ICAEW reported in May 2026 that the government’s late payments Bill, which is not yet law and may change, would include a 60-day cap on payment terms for large firms paying smaller suppliers if enacted in its current form. Before you lengthen DPO through supplier terms, check what those limits mean for your own contracts.

Frequently asked questions

How do you calculate AP days?

Divide average accounts payable by COGS or by purchases, then multiply by the number of days in the period, usually 365. You get the same answer by dividing 365 by the AP turnover ratio, provided both versions use the same numerator and the same average balance.

What is the AP turnover ratio formula?

AP turnover equals net credit purchases divided by average accounts payable. Net credit purchases means supplier invoices posted on account, less returns and allowances, and it includes overhead spend as well as inventory.

How do you calculate average accounts payable?

Add the opening and closing AP balances for the period and divide by two. If seasonal buying pushes payables well above or below those two dates, average the month-end balances so the figure reflects the whole year.

Should you use COGS or net credit purchases?

Use net credit purchases whenever you have access to the ledger, because it matches the invoices that actually create payables. COGS is an accepted proxy when purchases are not available, which is common when analysing another company’s published accounts. COGS leaves out overhead invoices and shifts with inventory movements, so state which basis you used.

What is a good AP to AR ratio?

The next step is to read the AP to AR ratio as a trend alongside DPO and days sales outstanding, and to compare it with businesses in your own sector. CFI’s guidance on AP days points the same way. Healthy payables days sit in line with industry norms and agreed supplier terms, and a rapid rise beyond those norms can signal cash flow stress.