How an Australian business should document a supplier overpayment and request reimbursement

If your business in Australia has paid a supplier more than it owed, act quickly: preserve proof of the transfer, confirm the excess is genuinely an overpayment, then send a single clear written request attaching the evidence and a reasonable repayment deadline. That approach protects your position, helps the supplier correct accounting or GST entries if needed, and gives you options — banking remedies, mediated dispute resolution, or formal recovery — if the payment is not returned.

The rest of this article explains what records matter, how to structure the written request, what to do if the payment went to the wrong account, the GST and tax consequences to watch for, and when to involve dispute services or legal help. The guidance draws on official Australian sources for business disputes, banking reversal limitations, and ATO rules on correcting GST.

Preserve and assemble the evidence you will actually need

The single most useful step is to gather contemporaneous records so you can prove the payment and its context. Keep: the bank or card statement showing the amount, date and reference; the invoice you paid and any credit notes; the payment confirmation or screenshot; internal authorisation notes showing who approved the payment; and any emails or changed billing details you received from the supplier.

Why these items matter: the bank statement proves the transfer occurred; the invoice proves what it was for; and authorisation records show whether the payment was an operational error. Practical guidance from state business authorities recommends preserving these items immediately — delays can make reversal or proof harder. See the NSW Small Business Commissioner’s advice on protecting payments and checking account details for the kind of records to save: Protecting your business from scammers | NSW Small Business Commissioner.

Confirm you really paid too much before you demand repayment

Before sending a reimbursement request, check the contract and the invoice terms. Look for agreed credits, retainers or holdbacks, different GST treatments, or earlier adjustments that could explain the difference. The national business guidance on supplier relationships notes that some apparent overpayments reflect agreed credits or timing differences rather than an error: Suppliers | business.gov.au.

If GST is involved, the tax effects are technical. The supplier may need to revise activity statements or issue an adjustment note and the ATO’s published materials describe how reimbursements and GST corrections interact; these rules affect whether the supplier or the Commissioner adjusts GST and how a recipient corrects any input tax credit claimed. Consult the ATO guidance on refunds of GST and GST determinations when the numbers involve GST: PS LA 2002/12 - Refunds of GST and Goods and Services Tax Determination.

Drafting a clear written reimbursement request: what to include and why it works

A single, professional written request (email is usually fine; registered post is an option for proof) should: identify the invoice and payment by date and reference; state the overpaid amount and how you calculated it; attach supporting documents (bank statement excerpt, invoice, payment confirmation); propose how the supplier can repay (bank transfer to a specific account or cheque) and give a reasonable deadline for reimbursement; and explain what you will do next if the payment is not returned (for example, request mediation or pursue debt recovery).

Keep tone factual and avoid inflammatory language. The Australian Small Business and Family Enterprise Ombudsman recommends mediation pathways and clear documentation for business-to-business disputes; a well-presented written request makes mediation more likely to succeed: Dispute support | ASBFEO.

Practical timing note: state nothing in the letter that assumes a legal outcome; present the claim, the evidence, and a reasonable time to resolve it.

If the payment went to the wrong account or the supplier’s details changed

If you suspect the funds were sent to an incorrect account or the recipient provided different bank details shortly before payment, contact your bank immediately. Banks can sometimes freeze or recall funds, but their ability to reverse transfers is limited and time-sensitive. State business offices emphasise rapid contact with your bank and the relevant authorities in these situations: Protecting your business from scammers | NSW Small Business Commissioner.

Also consider a police report or a report to national consumer regulators if there are other signs of wrongful conduct — those reports can help if a bank or insurer asks for evidence to support a recall request. Keep records of all contacts with the bank: the adviser’s name, date and time, and any reference numbers.

GST and tax consequences you must plan for

When an overpayment includes GST, correcting the amounts affects both parties’ activity statements. Typically the supplier will revise its returns or issue an adjustment note, and a buyer who claimed an input tax credit on the incorrect GST must correct its own reporting or use small-error correction rules if eligible. The ATO material explains when adjustments and refunds are available and that outcomes depend on the facts rather than being automatic: PS LA 2002/12 - Refunds of GST.

For larger sums or complex trading relationships, obtain an accountant’s advice or contact the ATO to clarify how to make the necessary corrections.

When the supplier disputes the claim or does not return the funds

If the supplier disputes liability or refuses to cooperate, first offer mediation through your state Small Business Commissioner or ASBFEO’s dispute support. These services specialise in business-to-business payment disputes and can be a lower-cost way to resolve matters without court: Dispute support | ASBFEO.

If mediation fails or the amount is large, you may need formal debt recovery, a demand letter from a lawyer, or court proceedings. Those options have costs and procedural rules that differ by state and court. If insolvency is a concern (the supplier is in receivership or liquidation), seek legal advice promptly; recoveries in insolvency are constrained by priority rules.

Note: different rules apply when an overpayment concerns employee wages — consult the Fair Work Ombudsman before taking action against payroll overpayments: Overpayments - Fair Work Ombudsman.

A brief worked example

Imagine you paid $11,000 on 1 September for an invoice showing $10,000 plus $1,000 GST. On 5 September you discover the supplier had previously agreed to accept $10,500 (including GST). Gather the bank record for the $11,000, the invoice, and any written agreement for $10,500. Send a dated written request showing the math, attach the documents, propose repayment to your nominated account within 14 days, and flag mediation through your state commissioner if the supplier does not respond. If GST correction is needed, both sides should coordinate how the supplier will revise its activity statement and how you will correct any input tax credit, referring to the ATO guidance above.

Practical next steps

1. Preserve the payment evidence now: bank statement, invoice, approvals. (See NSW guidance: Protecting your business from scammers | NSW Small Business Commissioner).
2. Confirm the overpayment and check GST implications against the ATO guidance: PS LA 2002/12 - Refunds of GST.
3. Send one clear written request with evidence and a reasonable deadline; if unresolved, seek mediation through ASBFEO or your state Small Business Commissioner: Dispute support | ASBFEO.

A professionally prepared, well-documented written demand can clarify the facts and make mediation or recovery more straightforward. If you want external help preparing a clear demand based on the documents you hold, consider a professional document-preparation service that converts your information into a formal request: .

This article has explained the documentary steps that preserve your position, the sensible contents of a written reimbursement request, the bank and ATO considerations to expect, and the dispute-resolution options available in Australia.

For help preparing a professional demand letter, BeforeSuit can help you prepare your next steps.