ATO assessment objections: deadlines, grounds and next steps

Identify the decision and the right process

An audit letter is not necessarily an objectionable assessment. A routine return error may be suitable for an amendment request. Keep the assessment, original assessment if amended, proof of service, audit reasons and any separate penalty decision together. Different decisions can require separate grounds and deadlines.

Objection time limits

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Decision	General rule	Check carefully
Original income-tax assessment	Two years where the specified two-year assessment category applies; otherwise four years from notice being given.	Taxpayer and assessment category under section 170; exceptions matter.
Amended income-tax assessment	Later of the original objection deadline and 60 days after service of the amendment.	An amendment does not reopen every item in the original assessment. Section 14ZV limits the scope.
GST assessment	Generally four years and one day after notice is given.	Amended assessments generally use the later of the original limit and 60 days. Separate input-tax-credit time limits may affect relief.
Other objectionable decisions	Often 60 days, but there is no universal deadline.	Use the specific provision and notice.
Late objection	Lodge the objection with a written extension request.	Explain the delay fully. Acceptance is discretionary.

Illustrative amended-assessment timeline

Assume an income-tax assessment was given on 15 October 2024 and has a two-year objection period. An amended assessment is served on 1 October 2026. The original deadline is 15 October 2026; 60 days after 1 October is 30 November 2026. The later date governs the objection to the amendment, subject to the scope rules. This example assumes valid service and no special rule.

15 October 2024 — original assessment given
1 October 2026 — amendment served
15 October 2026 — original two-year period ends
30 November 2026 — later amended-assessment deadline

Draft grounds fully and in detail

Section 14ZU requires grounds to be stated fully and in detail. Identify each disputed amount, the applicable provision, facts satisfying it and the replacement result. An unsupported statement that the ATO is wrong is not a useful ground. Include alternative arguments where appropriate and explain adverse evidence.

Grounds-of-objection framework

Decision: taxpayer, period, notice date and disputed item.
Result sought: corrected taxable income, tax or penalty and supporting calculation.
Ground: the specific legal or factual error.
Material facts: a numbered chronology relevant to the statutory test.
Evidence: an indexed document reference for each disputed fact.
Application: why the provision produces the result sought.
Alternatives: other grounds, penalty remission and any extension request.

This is an organising framework, not a completed objection or substitute for the approved form.

Payment, interest and recovery

Objecting does not automatically stop payment obligations or collection. Address undisputed amounts, cash flow, general interest charge and any recovery action separately. Ask the ATO to confirm any deferral or payment arrangement in writing. Interest can continue, and remission is not guaranteed.

The ATO’s published dispute-payment guidance includes a conditional 50:50 arrangement: payment of at least half the disputed amount and treatment of undisputed debt can support a request to defer recovery of the balance. It is an arrangement to seek, not a statutory entitlement or automatic interest waiver. Check current eligibility and the written terms.

What happens after lodgement?

The ATO considers the grounds and evidence and may request further information. Keep the response consistent with the objection and explain any corrections. Preserve a complete lodged copy, attachments and acknowledgement.

Section 14ZYA permits a written notice requiring a decision after the relevant initial 60-day period has expired. A timely information request can affect when that period ends; accepted late objections also have specific timing. If the ATO still does not decide within 60 days after the notice, the objection is deemed disallowed. This opens a review pathway; it is not a deemed win.

ART or Federal Court after disallowance

For qualifying objection decisions, an ART review application or Federal Court appeal generally must be lodged within 60 days after service of the objection decision. The ART replaced the AAT on 14 October 2024. Check the particular decision’s rights, grounds, extension rules and costs before choosing a forum.

The ART undertakes merits review. A Part IVC Federal Court appeal is a statutory tax proceeding, not simply a complaint about unfair administration. The taxpayer’s burden and restrictions on grounds matter in both routes. Court proceedings also bring formal evidence and adverse-cost exposure; specialist advocacy may be proportionate.

DIY, accountant or lawyer?

A clear calculation issue may be handled by you or your tax agent. Consider legal advice where the dispute turns on interpretation, credibility, anti-avoidance, privilege, significant penalties or a related transaction. Before paying for extensive drafting, obtain a view on prospects, missing evidence and the value of the relief sought.

Frequently asked questions

Does an amended assessment give me another four years?

Not automatically. The usual rule is the later of the original objection deadline and 60 days after service of the amended assessment. Scope restrictions also apply.

Can I object late?

You can request an extension when lodging the objection and explain the circumstances and reasons for delay. The ATO must decide whether to accept it.

Does paying mean I accept the assessment?

Paying does not by itself abandon objection rights. Preserve the objection deadline and obtain advice on any settlement or release before agreeing to it.

Official sources

General information as at 29 September 2026, not advice about your circumstances. The applicable law, documents and dates need to be checked before you act.