Invoice Fraud and Billing Schemes

Invoice fraud is any attempt by an external party or internal employee to cause a business to pay money it does not legitimately owe. Billing schemes are a subset of invoice fraud that originate from within the organisation -- where an employee creates or manipulates invoices to extract money for themselves or an accomplice. Together, invoice fraud and billing schemes represent the largest category of financial loss for Australian businesses that pay supplier invoices at volume.

The Association of Certified Fraud Examiners estimates that billing schemes account for around 22 percent of all occupational fraud cases and cause a median loss of AU$130,000 per incident before detection. Detection time averages 24 months. That combination -- large losses and slow detection -- makes AP fraud the most financially damaging category of fraud that most businesses never plan for explicitly.

Common invoice fraud variants

The most common form of external invoice fraud targeting Australian businesses is the false invoice, where a supplier -- real or fictitious -- submits an invoice for goods or services that were never delivered, or inflates the value of what was delivered. False invoices are most effective when the business lacks a purchase order matching process, because there is no agreed amount to compare the invoice against.

Overpayment fraud involves submitting invoices at values higher than what was agreed, often by small amounts that fall below the threshold that would trigger additional scrutiny. If an approved supplier normally invoices at AU$4,800 per month, an invoice at AU$5,100 may pass through a one-person approval without question. Repeated across 12 months, that is AU$3,600 extracted through a control gap.

Duplicate invoice fraud submits the same legitimate invoice more than once -- sometimes months apart, sometimes through different submission channels such as email and a supplier portal, to reduce the chance of a manual match. Without automated duplicate detection, these payments are often only discovered during an annual audit or supplier statement reconciliation.

How billing schemes work from inside the business

Internal billing schemes require the fraudster to have some level of access to either the AP process or the vendor master file. The three most common structures are: shell company schemes, where an employee creates a fictitious vendor and submits invoices from it; personal purchase schemes, where an employee routes personal expenses through the AP system by coding them to operating expense accounts; and payroll abuse through the AP ledger, where contractor payments are inflated or fictitious contractors are added.

Shell company schemes are particularly difficult to detect without vendor master controls because the "supplier" often has a legitimate-looking ABN, a real bank account, and invoices formatted to look plausible. Australian business registrations are public and cheap, making it straightforward for a fraudster to register a company and begin invoicing through it within days.

Detection and prevention

The most effective controls against invoice fraud and billing schemes operate at the point of entry into the AP process. Automated duplicate detection flags invoices with matching amounts, dates, or invoice numbers before they are approved. Purchase order matching requires every invoice to reference a pre-approved purchase order before it can proceed through the workflow. Vendor master change controls require dual sign-off and notification before any banking details are updated on an existing supplier record.

Segregation of duties -- ensuring that no single person can create a vendor, approve an invoice, and authorise a payment -- removes the single point of control that most internal fraud schemes rely on. In small AP teams where segregation is difficult, compensating controls such as independent payment file review and monthly AP ledger analysis by a senior manager provide a meaningful reduction in exposure.

Regular supplier statement reconciliations surface discrepancies between what a supplier says they are owed and what the AP system shows. These discrepancies are often the first visible sign of a duplicate payment or an invoice that was processed internally but never received by the supplier -- both of which are worth investigating promptly.