Short answer
If you've already lodged but realised you forgot income, you should amend your tax return as soon as possible — voluntary disclosure carries significantly lower penalties than waiting for the ATO to catch it.
The ATO matches your declared return against ~600 million data records every year: bank interest, dividends, employer PAYG, share trade summaries, crypto exchange data, Centrelink, health insurance, rental income via real-estate agents. If you forgot something they have data on, they will notice — usually within 12-18 months.
What "voluntary disclosure" means and why it matters
The ATO penalty regime sliding scale:
| Scenario | Penalty (% of shortfall amount) |
|---|---|
| Genuine mistake, voluntary disclosure before audit | 0% (just pay the shortfall + interest) |
| Genuine mistake, after ATO contact | 25% |
| Failure to take reasonable care | 25% |
| Recklessness | 50% |
| Intentional disregard | 75% |
| Above + voluntary disclosure before audit | Reduced 80% |
Translation: amending yourself before the ATO contacts you ≈ no penalty. Waiting for ATO to find it ≈ 25-75% penalty on top of paying the actual tax owed.
How to amend your tax return
Option 1: myTax (within 2 years of original lodgement)
Option 2: Paper amendment
Use form NAT 2843 if myTax doesn't show "Amend" (older returns, complex cases, or if you're outside the 2-year self-amendment window).
Option 3: Through your Tax Agent
If a Tax Agent lodged your return, they handle the amendment — usually faster and cleaner, and they negotiate any penalty position with the ATO on your behalf.
Common "forgot income" scenarios
Timeframes
| Scenario | Amendment window |
|---|---|
| Individual return, normal cases | 2 years from notice of assessment |
| Individual return, significant change | 4 years (longer for tax avoidance) |
| Business / complex cases | 4 years |
| Fraud or evasion | No limit |
Past the standard window, you can apply for an extension or use the "objection" pathway — much more involved.
When you should use a Tax Agent
Amend yourself in myTax if:
- The missed amount is small (under $500-1000)
- It's a single category (just bank interest, or just one missed Uber payment)
- You're confident on the recalc
Use a Tax Agent if:
- Missed amount is significant (> $2,000)
- ATO has already contacted you ("we noticed your return missed XYZ")
- It's the result of multiple missed items
- You think you might owe shortfall interest + penalty negotiation
- You have CGT events, foreign income, or trust distributions involved
Need a professional? Browse every TPB-registered tax agent near you in the AusTax directory, or post a request and matching practices will contact you — free.
See main decision guide for the broader framework.
Need Help With Your Tax Return?
Complex situation? a registered tax agent (see the directory) Our partner agents review every detail for accuracy and compliance.
*Disclaimer: This is general information only and does not constitute personal tax advice. Consult a registered tax agent for advice tailored to your specific situation. Always verify against the latest ATO guidelines at ato.gov.au.*
This is general information only. For amendments with potential penalty exposure, engage a TPB Registered Tax Agent — they can manage the ATO conversation and minimise penalty.