Sole Trader Tax in Practice — Quarterly BAS, GST and PAYG Instalments
A rundown of the ongoing tax obligations a sole trader working under an ABN must keep meeting after starting up. Covers the GST registration threshold ($75,000) and tax invoice requirements, quarterly BAS due dates and failure-to-lodge penalties, how PAYG instalments work, and 5-year record keeping.
Sole trader tax is not a one-off — it is ongoing
Getting your ABN and opening for business is not the end of it. A sole trader has no employer withholding tax from their pay, so you must manage GST, income tax and record keeping entirely on your own — and the obligations repeat every quarter and every year, not just once. The key point is that lodgment obligations pile up quietly. The moment you register for GST, you must lodge a BAS every quarter, and once you lodge your first tax return, the ATO starts issuing PAYG instalment notices. Not knowing is no exemption, and missed lodgments can attract penalties. This guide lays out that recurring cycle at a glance.
Scope of this guide — how it relates to the other guides
How to tell whether work is in substance that of an employee or a contractor, and an overview of the ride-share GST special rule, are covered in the Gig Work and ABN Contracting guide; start-up steps such as ABN and business name registration are covered in the Starting a Business guide. Tax deductions for employees are handled by the Employee Tax Deductions guide and follow different rules from business expenses. This guide is dedicated to the 'ongoing compliance' of a sole trader who has completed registration — GST, BAS, PAYG instalments and record keeping — and is a general explanation of the system, not tax advice for individual circumstances.
GST registration — when it becomes compulsory and what changes
GST (Goods and Services Tax) is Australia's 10% value-added tax. You must register within 21 days once your annual turnover (GST turnover) reaches $75,000 ($150,000 for non-profit organisations) or is expected to reach it within the next 12 months. There is one exception — ride-share and taxi driving requires registration from the first dollar, regardless of turnover. Once registered, you charge prices with GST included, claim back GST paid on business purchases as credits, and settle up each quarter through the BAS.
Tax invoice requirements — registration changes your invoices
After registering for GST, you must issue a tax invoice within 28 days if the buyer requests one for sales of $82.50 (including GST) or more. The required details are the words 'Tax invoice', the seller's business name and ABN, the date of issue, a description, quantity and price of the items sold, and the GST amount (or the words 'Total price includes GST'); sales of $1,000 or more must also include the buyer's business name or ABN. Follow the ATO's official guidance for the detailed format requirements.
- Review your last 12 months' actuals and next 12 months' projected turnover every month — the obligation starts from the point reaching $75,000 becomes 'expected'
Quarterly BAS lodgment — what you need and when it is due
The BAS (Business Activity Statement) is the form GST-registered businesses use to report and settle GST (plus PAYG withholding and PAYG instalments where applicable); most small sole traders are on a quarterly cycle. The standard due dates are 28 October for July–September, 28 February for October–December, 28 April for January–March, and 28 July for April–June. Lodging electronically or through a registered tax agent may give extra time for some quarters, so check the exact due dates that apply to you in ATO online services.
- A myGov account linked to ATO online services (or your accounting software's electronic BAS lodgment feature) — faster than paper and better for managing deadlines
- Books, receipts and invoices that let you total the GST included in the quarter's sales (1A) and the GST credits on business purchases (1B)
PAYG instalments — the first-year tax shock and how instalments work
Employees have tax withheld from their pay, but no one withholds anything from a sole trader's business income. That creates the trap where your first year's income tax is billed all at once at the next year's tax return, and from then on the ATO moves you into PAYG instalments, a quarterly pre-payment system. It is easiest to understand in four phases.
In your first financial year (1 July – 30 June) there is usually no instalment notice. Instead, a full year's tax is billed in one hit after the following year's tax return. Setting aside your estimated tax in a separate account whenever income comes in is your only defence.
If the business and investment income in your first tax return exceeds the threshold, the ATO automatically enters you into PAYG instalments and notifies you via myGov or post. From then on you usually pay the notified instalment each quarter; if you lodge a BAS, it appears on your BAS as well.
You can enter early yourself via ATO online services without waiting for a notice. Spreading payments from the first year reduces the crunch of 'last year's tax in one hit plus this year's instalments' landing together.
If your income changes, you can vary the instalment amount or rate. Instalments you have paid are credited in full against your final tax in the year-end tax return, and any excess is refunded. But if you vary too far below the actual figure, interest may apply to the shortfall.
Five record-keeping and money-management habits
Half of tax compliance is record keeping. The ATO generally requires you to keep evidence of income and expenses for 5 years, and good records make BAS preparation, deduction claims and substantiation all easier. Make these five things a habit.
- Keep a separate business-only bank account — not a legal requirement for sole traders, but it makes BAS totals and expense substantiation dramatically easier
- GST you collect is not your money — when GST-inclusive sales land in your account, move the GST portion (1/11 of the price) straight into a separate account
Five common mistakes — they build up quietly, then hit all at once
Most sole trader tax troubles come not from 'not knowing' but from putting things off until 'later'. These five are the most frequently repeated mistakes.
- Delaying GST registration after turnover passes $75,000 — you can be made to pay GST you never even collected, backdated to when the obligation began, plus penalties
- Not lodging a nil BAS for a quarter with no transactions — the failure to lodge (FTL) penalty can apply even when there is zero tax to pay
- Spending the GST you collected and your income tax share on living costs — the classic failure pattern of having no cash when the quarterly BAS and year-end tax return payments fall due
Useful official links
- ATO — GST 등록 (Registering for GST)(opens in a new window)
The official ATO page explaining the GST registration threshold ($75,000, including the special rule for ride-share), how to register, and your obligations after registering.
- ATO — BAS (Business Activity Statements)(opens in a new window)
The official ATO guide covering the BAS end to end — how to lodge and pay, quarterly due dates, nil lodgment, and amendments.
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