Deadlines, Pitfalls and Official Sources
Common tax return mistakes in Australia and the official sources to check
The individual tax return errors that most often trigger ATO adjustments, what happens if you get it wrong, how to avoid scams, and a directory of official sources.
The tax return mistakes that most often lead to an ATO adjustment for individuals are: leaving out income the ATO already knows about (interest, dividends, capital gains, crypto, rental income, a second job), claiming deductions without records or with private use included, claiming costs that were reimbursed, missing the notice of intent for personal super contributions, lodging before pre-fill is complete, and using the wrong residency status. The ATO matches returns against data from employers, banks, share registries, crypto exchanges, property managers, health funds and government agencies, so omissions are often found. Getting it wrong usually means an amended assessment, interest and sometimes a penalty; correcting it yourself early limits the cost.
This is the pillar guide for the deadlines and pitfalls section. It summarises the mistakes, explains the consequences and lists the official bodies to use. Each topic links to a detailed guide. It is general information, not tax advice.
The mistakes, grouped
| Area | Mistake | Why it happens | Detailed guide |
|---|---|---|---|
| Income | Omitting interest, dividends, ETF distributions or a second job | Lodging before pre-fill is complete | Documents checklist |
| Income | Ignoring capital gains on shares or crypto, including crypto-to-crypto swaps | Belief that only cashing out counts | Selling shares example |
| Deductions | Claiming without records, claiming private use, claiming reimbursed costs | Copying last year's figures or "everyone claims it" | Work-related deduction mistakes |
| Deductions | Working from home: estimated hours, or phone and internet claimed on top of the fixed rate | Rules changed in 2023 | WFH methods |
| Rental | Capital improvements claimed as repairs, interest on private redraws claimed, wrong ownership split | Complexity of rental rules | Negative gearing example |
| Super | No acknowledged notice of intent; exceeding caps | Contributions made late in June | Exceeding super caps |
| Timing | Missing 31 October without being on an agent's list | Assuming the agent deadline applies automatically | Deadlines and agent lodgment |
| Payments | Not paying by the due date, or not lodging at all because of a debt | Fear of the bill | Late lodgment penalties |
| Fixing | Not amending when an error is found | Not knowing the process | Amendments, objections and complaints |
What happens if the ATO finds an error
- A query or review. The ATO may contact you to explain a discrepancy, often triggered by data matching or a claim that looks high compared with others in the same occupation and income range.
- An amended assessment. The ATO adjusts the income or deduction and issues a new notice. Any extra tax is payable by the due date shown.
- Shortfall interest charge on the extra tax from the original due date to the amended assessment, and the general interest charge if the amount is then paid late.
- Administrative penalties for a tax shortfall can apply, generally as a percentage of the shortfall depending on behaviour: 25% for failing to take reasonable care, 50% for recklessness and 75% for intentional disregard, with reductions if you tell the ATO before it starts an examination. Penalties for minor errors made despite reasonable care are often not applied.
Since 1 July 2025, interest charges such as GIC and SIC are reported to be no longer tax deductible, so the true cost of a late payment has risen. Check the ATO page on interest charges for the current treatment.
Scams to watch at tax time
Criminals impersonate the ATO and myGov, especially from July to October.
- Treat any SMS or email with a link asking you to log in to myGov or "claim a refund" as suspicious. The ATO has said it no longer includes links in unsolicited SMS and emails asking you to log in.
- The ATO will not demand payment by gift card, cryptocurrency or a transfer to a personal account.
- Log in by typing my.gov.au yourself, and set up a myGov passkey or strong authentication.
- Tax agents must be registered. Check the Tax Practitioners Board register before giving anyone your myGov or bank details.
- If you think your identity has been compromised, contact the ATO and IDCARE (Australia's national identity and cyber support service).
Directory of official sources
| Body | What it does for you | Website |
|---|---|---|
| Australian Taxation Office (ATO) | Rates, thresholds, myTax, rulings, payment plans | ato.gov.au |
| myGov | Secure access to ATO online services | my.gov.au |
| Tax Practitioners Board (TPB) | Register of tax and BAS agents; complaints about agents | tpb.gov.au |
| Inspector-General of Taxation and Taxation Ombudsman | Independent complaints about the ATO | igt.gov.au |
| Administrative Review Tribunal (ART) | External review of many ATO decisions (replaced the AAT in October 2024) | art.gov.au |
| The Treasury | Budget measures and consultations on proposed changes | treasury.gov.au |
| Federal Register of Legislation | Tax Acts as in force | legislation.gov.au |
| StudyAssist | HELP and study loan rules | studyassist.gov.au |
| Services Australia | Medicare entitlement, Centrelink payment summaries | servicesaustralia.gov.au |
| Moneysmart (ASIC) | Independent guidance on money, super and investing; adviser register search | moneysmart.gov.au |
The ATO also runs free Tax Help for eligible people on lower incomes during tax time, staffed by trained volunteers. Check the ATO site for eligibility and locations.
When to consult a professional
Consider a registered tax agent if you: sold an investment property or a large share portfolio; have foreign income or changed residency; received an ATO audit letter; have several years of unlodged returns; run a business or receive trust distributions; or are making large super contributions near the caps. For investment or super strategy, a licensed financial adviser can give personal advice that this site cannot.
FAQ
How far back can the ATO amend my return?
For most individuals with simple affairs, two years from the date of the notice of assessment; four years for many others; and no time limit in cases of fraud or evasion.
Will I be penalised for an honest mistake?
If you took reasonable care, a shortfall penalty is less likely, but you still pay the extra tax and usually shortfall interest. Voluntarily correcting it helps.
Does using a tax agent protect me?
You remain responsible for your return. If you gave the agent complete information and they made an error, you may not be liable for a penalty (safe harbour), but you still pay the tax.
Where do I check whether a tax change has passed?
The ATO's new legislation pages show whether a measure is law; Treasury pages show proposals; the Federal Register of Legislation shows enacted text.
Sources
- Australian Taxation Office — common errors, data matching, penalties and interest, scams
- Tax Practitioners Board — registered agent search
- Inspector-General of Taxation and Taxation Ombudsman — complaints about the ATO
- IDCARE — identity and cyber support
