The Fine Print Australia · PUBLISHED 27 JUN 2026 · VERIFIED 27 JUN 2026 · AU EDITION

ATO Side Hustle Tax Rules: Why the $18,000 Threshold Is a Trap 🇦🇺

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Australians can be required to declare side-hustle income even when it is paid through digital platforms or merchant channels that the ATO can already see, so “small” undeclared gigs are no longer invisible.

The number that matters

The central number is $75,000, the GST turnover threshold at which a business generally must register for GST in Australia; the ATO’s side-hustle guidance says businesses may need GST registration depending on turnover, and secondary tax-compliance explanations commonly anchor the threshold at $75,000.

How it quietly costs you

The first money leak is failing to declare side-hustle income because people think it is a hobby, not a business. The ATO says there is no fixed dollar threshold for being “in business”; instead, it looks at whether the activity is continuous, repeated, and profit-seeking, and if so the income must be declared.

The impact is straightforward: all income from a side hustle must be included in the tax return, even if it is earned through an app, website, or platform, and the ATO has expanded data matching with sharing-economy and marketplace platforms.

The “old vs better” comparison is:

• Old/unsafe: assuming cash, app, or marketplace payments are too small or too fragmented to matter.
• Better: treating the activity as taxable business income when it is repeated, organised, and profit-seeking, and keeping records from day one.

The second, compounding trap

The second layer is deductions and compliance costs that compound once the activity is classified as a business, especially GST, record-keeping, and possible instalments. The ATO says side-hustle operators may need an ABN, may have to register for GST, and may be pushed into more formal reporting depending on structure and turnover.

The long-run cost of inaction is that people can end up paying tax late on income they should have been setting aside, while also missing deductible expenses because they did not keep records. The ATO requires accurate records for tax purposes, and commentary on the ATO’s compliance approach notes records should be kept for five years.

A concrete threshold effect is the $75,000 GST-registration point, which turns a casual income stream into a more formal tax and compliance obligation if turnover rises.

What this looks like in practice

Mia, 34, is a Brisbane marketing coordinator earning $82,000 salary, with a Depop/eBay side hustle bringing in $18,000 a year from reselling clothes and accessories; she plans to keep doing it for 15 years before retirement.

She would discover:

• Her side hustle is likely taxable business income, not a hobby, because the ATO looks for continuous, repeated, profit-seeking activity rather than a dollar threshold. Her $18,000 is not too small to matter if the activity is business-like.
• She may be able to deduct legitimate business expenses, such as platform fees and supplies, but only if she keeps proper records; the practical difference is between paying tax on gross receipts versus net profit.
• If turnover grows to $75,000, she would cross the GST-registration threshold, which changes compliance significantly compared with staying below that level.

The full cost of doing nothing

For Mia, the combined lifetime effect of undeclared income plus lost deductions can be material: if her $18,000 side hustle continues for 15 years, the cumulative gross turnover is $270,000 before growth. Using the ATO’s business-in-business test and the GST threshold as the modeling basis, the main risk is that taxes and records problems compound over time rather than appearing in one year.

What to do about it

• Check whether the activity is actually a hobby or a business using the ATO’s side-hustle guidance and business indicators. The relevant ATO figure is the absence of a fixed dollar threshold and the focus on continuous, repeated, profit-seeking conduct.

• Go to the ATO’s side-hustle guidance page.

• Compare your activity against the ATO indicators: profit intent, repetition, and business-like conduct.

• Write down whether you are selling personal items or actively sourcing inventory/customers.

• Good looks like: you can clearly explain why the ATO would treat it as either a hobby or a business.

• Record all income and expenses in a dedicated file before you lodge. The ATO says accurate records are required, and business records generally need to be kept for five years.

• Open your bank, app, and marketplace statements.

• Export sales, fees, postage, supplies, and receipts.

• Put them in one folder or spreadsheet by tax year.

• Good looks like: every dollar in and every deductible dollar out is traceable.

• Estimate whether GST and ABN obligations apply if turnover is growing. The key benchmark is the $75,000 GST threshold.

• Add up expected annual turnover from the side hustle.

• Compare it with $75,000.

• If you are approaching the threshold, review ABN/GST registration needs in ATO tools and guidance.

• Good looks like: you know whether you are safely below, near, or above $75,000.

A myth worth clearing up

Myth: “If the side hustle is small, cash-based, or through an app, the ATO won’t see it.” Fact: The ATO says side-hustle income must be declared when it is business income, and it has broadened data matching with platforms and financial channels, so undeclared income is increasingly visible.

Sources

• AUSTRALIAN TAXATION OFFICE
• AUSTRALIAN TAXATION OFFICE

Researched 2026-06-27.

Corrections & disclosure: an AI-assisted, human-reviewed guide. Every figure is dated and sourced above. Spot something out of date or wrong? Tell us and we’ll correct it — corrections are noted here and in the video description.