The AU$27.67 figure is the one most businesses encounter when researching AP automation costs in Australia. It’s the ATO’s benchmark for what it costs to process a manually handled B2B invoice - often referred to as the cost per invoice - including staff time for data entry, coding, approval routing, and exception resolution. At 100 invoices per month, that’s AU$2,767 in processing labour. Annualised: AU$33,204.
This is the number that makes the automation business case arithmetic look straightforward. A platform costing AU$400 per month that reduces processing labour by 60% pays for itself in weeks.
But the AU$27.67 figure describes the successful processing of a normal invoice. It doesn’t count the invoices that aren’t normal - and in manual AP, more invoices than you’d expect aren’t normal.
What does the benchmark not include?
An invoice that needs to be rekeyed because the first entry had the wrong supplier selected: another 10-15 minutes. A duplicate invoice that cleared approval and was paid, discovered six weeks later when the supplier sent a statement: recovering the credit note, processing the reversal, updating the ledger - typically 45 minutes to two hours, plus whatever the supplier’s credit terms say about how the overpayment gets applied. A GST coding error found at BAS time: correcting the journal, lodging the amendment, potential ATO correspondence - variable, but never less than an hour.
None of this appears in the AU$27.67 benchmark because the benchmark describes successful processing, not exception processing. Exception processing is where most AP labour time actually concentrates in manual workflows.
For a business processing 100 invoices per month from 30 active suppliers, a 2-4% exception rate is realistic - two to four invoices per month where something needs correction after initial processing. At an average exception resolution time of 60 minutes, that’s 2-4 hours per month in correction work on top of the benchmark processing time. At a finance officer rate of AU$40 per hour, that’s AU$80-160 per month in additional cost that doesn’t appear in the standard calculation.
The error types that create financial exposure
Some AP errors cost only time. Others have direct financial consequences.
Duplicate payments are the most common financially material error in manual AP. A supplier submits an invoice twice - different reference numbers, slightly different formatting - and both are processed and paid. At 100 invoices per month from 30 suppliers, a 1% duplicate rate means one duplicate payment per month on average. If the average invoice value is AU$4,000, that’s AU$4,000 in overpayment. Recovery depends on the supplier’s cooperation and can take weeks. Some overpayments get applied to future invoices without notice, creating reconciliation problems months later.
GST coding errors accumulate quietly. An invoice miscoded as GST-inclusive when it’s GST-free overstates the input tax credit claimed on that BAS. Across 100 invoices per quarter, even a 3% miscoding rate means three invoices per quarter with incorrect GST treatment. The ATO doesn’t audit these routinely, but when a business goes through a tax review, a pattern of incorrect input tax credit claims creates a liability including the overclaimed amount, interest, and potentially penalties.
What fraud exposure does manual processing create?
Payment redirection fraud exploits the gap between invoice receipt and payment approval. An attacker sends an invoice or bank detail change request impersonating a known supplier. In a manual AP process, the check that would catch it - comparing the bank account number on the incoming invoice against the account stored for that supplier - depends on the accounts payable officer remembering to do it while processing 80 other invoices that month. Under time pressure, the check gets skipped. The payment goes to the wrong account. This is the AP fraud vulnerability that manual workflows leave wide open.
The ACCC’s National Anti-Scam Centre reported AU$152.6 million in payment redirection losses across Australian businesses in 2024. The losses concentrate in businesses with established supplier relationships and manual verification processes - precisely the profile of a 15-to-50-person Australian business with a manual AP workflow. A single successful fraud at AU$15,000 adds AU$15,000 to the real cost of manual AP for that business that year, plus the staff time investigating and attempting recovery. BECS payments are processed quickly, and reversal isn’t guaranteed once funds have moved.
The honest total
For a 20-person Australian business processing 100 invoices per month:
The AU$27.67 benchmark gives AU$2,767 per month in direct processing labour - AU$33,204 per year. Add exception correction labour at a 3% rate: approximately AU$120 per month. Add duplicate payment exposure - one duplicate per month at AU$4,000 average value, assume 75% recovery, equals AU$1,000 average net loss. Add fraud exposure, amortised conservatively: material, but highly variable.
The visible, calculable costs run to roughly AU$3,000-3,200 per month before fraud. Fraud exposure is harder to quantify in advance, but the ACCC data makes clear it isn’t hypothetical for businesses at this size and invoice volume.
AP automation for 100 invoices per month typically costs AU$300-500 per month and reduces direct processing labour by 60-70%. For a comparison of the available platforms, see our guide to the best AP automation software in Australia. At AU$400 per month, the net annual saving on processing labour alone is around AU$17,000. That’s before counting prevented duplicate payments and fraud exposure.
The business case for automating AP isn’t complicated. It’s usually presented as a time-saving argument, which undersells the error and fraud prevention components - and those are often where the more significant financial exposure actually sits.
Sources: ATO - E-invoicing and invoice processing in Australia · ACCC National Anti-Scam Centre - Targeting Scams Report 2024 · ASBFEO - Payment Times and Practices
Further reading: Best AP Automation Software Australia 2026 · What a Modern AP System Needs to Do · AP Automation: The Business Case for a 15-Person Business