Tax return mistake? Prepare the amendment evidence first

This guide helps an owner who has found missing income, a duplicate expense or another possible error after lodging. Keep a traceable record of the proposed correction and preserve what was originally submitted.

Preserve the original position

Save the lodged return, notice of assessment, supporting calculations and any later amendments. Record which entity the return belongs to and the income year. A company return and the owner's personal return may be connected, but they are separate records.

The ATO's before-you-amend guidance distinguishes correcting your return from querying an ATO processing error. It also says to wait for notification that the original return or a previous amendment has been processed before lodging another amendment. Record the current status rather than submitting a second correction blindly.

Explain each proposed change

Use one row per issue. Attach the missing invoice, corrected statement or calculation that supports it. Include the original document reference as well as the replacement. Describe what happened plainly: an invoice was omitted, a line was duplicated, or updated information arrived after lodgement.

In the example, the missing invoice still needs a recognition-period check. The income figure cannot be changed safely just because a document has a date in the year. Give the adviser the delivery, invoice and payment information needed to decide.

If a platform reconciliation revealed the difference, include its period bridge and transaction IDs. A revised total without the underlying reconciliation makes it harder to check the error.

Verify the pathway and time limit promptly

Amendment periods differ by taxpayer and circumstances. The current ATO individual and sole-trader time-limit guidance distinguishes income years for sole traders and links to separate business and superannuation guidance. Don't copy a generic deadline from another business's example.

Give the tax agent the date the assessment was sent, the income year, entity details and any prior amendment notices. Ask them to confirm the applicable deadline and pathway in writing. A disagreement with an ATO decision, an ATO processing error and your own omitted item may call for different action. An out-of-time request also needs specific advice.

This guide concerns income tax. If the same transaction affects a business activity statement (BAS), record that as a separate issue for the appropriate agent. The BAS agent versus tax agent guide explains the scope distinction.

Close the loop after submission

Keep the submission reference, final figures and agent's explanation together. When a new assessment arrives, compare it with the correction and update the ATO account reconciliation. If the result changes a payment or refund expectation, update the cash forecast rather than assuming the proposed amount is settled.

An expected refund can be affected by other tax debts, as the ATO explains. Wait for the actual outcome before treating it as available cash.

Key takeaways

• Preserve the original return and link every proposed change to evidence.
• Confirm the entity, income year and assessment status.
• Treat the amendment pathway and deadline as questions to verify promptly.

Where to get help

Use ATO amendment guidance and ask a registered tax agent to confirm the pathway and deadline for your actual assessment. Provide the evidence pack rather than only a revised total.