Australian GST and the BAS: the complete guide for 2026

GST is the largest single compliance task on an Australian small business calendar. The rate itself is simple (10% on most things), but the BAS cycle, the tax-invoice rules, the carve-outs for basic food, residential rent, and financial supplies, and the small forest of edge cases around government charges and bank fees combine to absorb hours of bookkeeper time every quarter. This guide covers what every Australian SMB owner and bookkeeper needs to know in 2026: the rate, the thresholds, the BAS due dates, the tax-invoice rules, and the specific edge cases ExpenseFlow handles at capture so they never reach the BAS. Every figure, deadline, and regulation in this guide is referenced to an official ATO or Australian Government source; full URLs appear in the Sources section at the end.

What GST is and how it works in Australia

GST, the goods and services tax, is a broad-based tax of 10% on most goods, services, and other items sold or consumed in Australia ^[1] . Businesses collect GST from their customers, pay GST to their suppliers, and remit the net amount to the ATO through the Business Activity Statement (BAS). The system is designed so the final consumer carries the tax; businesses in the middle of the supply chain pass it through, claiming credits for the GST they paid on their inputs.

There are three categories of sale plus the residual “not subject to GST” bucket ^{[1] [7] [8]} :

The line between GST-free and input-taxed matters and is invisible from the customer’s side (both show no GST). A GST-free supplier can still reclaim the GST it paid on its inputs; an input-taxed supplier cannot. The line between taxable and out-of-scope government charges matters because miscoding a government fee with 10% GST is a common BAS error: the practice claims an input-tax credit it is not entitled to. Both lines are the kind of judgment the AI reviewer makes at capture, before the data reaches the BAS.

The A$75,000 registration threshold

You must register for GST when your rolling 12-month GST turnover (gross income from all businesses you carry on, less GST) reaches A$75,000 ^[2] . For non-profit organisations the threshold is A$150,000. For taxi and ride-sourcing drivers (Uber, DiDi, Ola, and traditional taxi or limousine services), GST registration is required from the first dollar of fare income, no matter how small the operation ^[2] .

Registration is not optional once you cross the threshold. Once required, you have 21 days to register ^[2] . If you fail to register, the ATO can backdate your registration to the date you should have registered, and you owe the GST on the sales you made after that date, whether you collected it or not. Backdating is limited to 4 years (longer if there is fraud or evasion). The 21-day window catches a lot of growing businesses that pass the threshold during a busy quarter and only notice at year-end.

You can also choose to register voluntarily below the threshold. Voluntary registration suits a business whose customers are themselves GST-registered (they reclaim the GST you charge them, so the 10% does not raise your effective price) and whose own inputs carry significant GST you would like to recover. If your customers are end consumers, voluntary registration raises your effective price by 10% and is rarely worth it. Once you register voluntarily, you must stay registered for at least 12 months ^[2] .

The BAS: quarterly, monthly, or annual

The BAS is how Australian businesses report and pay GST (and PAYG instalments, PAYG withholding, FBT instalments, fuel tax credits, and several other taxes that share the same form). Your reporting cycle depends on your GST turnover ^[3] .

Quarterly is the default for any business with GST turnover under A$20 million that the ATO has not directed to report monthly. The four standard quarters and their self-lodge due dates are ^[3] :

The Q2 due date sits two months after the period end, not one. The extra month is a built-in extension for the summer holiday period, so no further extension applies for Q2. For Q1, Q3, and Q4, businesses that lodge their BAS online can claim a two-week deferral, taking the effective due date to 11 November, 12 May, and 11 August respectively ^[3] . The two-week deferral has terms and conditions that the ATO publishes; in practice it requires you to be a self-lodger using SBR-enabled software, the BAS to have been generated by that software, and the payment to be made through the same channel.

Monthly reporting is mandatory for any business with GST turnover of A$20 million or more, and optional for any business below that level ^[3] . The due date is the 21st day of the month following the end of the taxable period; a July monthly BAS is due 21 August. Some practices voluntarily move clients to monthly cycles when those clients have unstable cash flow, because smaller more frequent payments are easier to manage than one large quarterly bill.

Annual reporting is available to businesses that are voluntarily registered (turnover under A$75,000, or under A$150,000 for non-profits) ^[3] . The annual GST return is due by 31 October, or by 28 February if the business is not required to lodge an income tax return.

Practices lodging on behalf of clients through a registered tax or BAS agent generally receive an extended lodgement program from the ATO, with deferral dates that depend on the agent’s program for that quarter. Talk to the practice principal for the specific dates this year.

Registration: when, how, and what to expect

Registering for GST in Australia takes about 20 minutes online if you have your business documents to hand. You will need your Australian Business Number (ABN), the date you started or will start the activity that triggers registration, your expected turnover for the next 12 months, the BAS reporting cycle you want (quarterly, monthly, or annual), and bank-account details for payments to and from the ATO ^[2] .

There are three lodgement channels: Online services for business (the ATO’s own portal), registered tax or BAS agent (who can lodge on your behalf), or phone on 13 28 66 ^[2] . Most businesses register online or through their agent. After submission, the ATO usually confirms registration within a few business days, though longer waits happen during peak periods.

A common error is to start charging GST before the registration is confirmed. The correct approach is to raise your prices to cover the GST during the gap and then re-issue tax invoices (or issue an adjustment) to your customers once the registration is effective. Charging “GST” without being registered is not legally GST and is not recoverable by your customers.

The opposite error catches businesses that grow through the threshold without noticing. The 12-month turnover test is rolling, not financial-year. A business that hits A$75,000 in cumulative sales over the May-to-April window is required to register, even if it would not hit A$75,000 in any individual financial year. The dashboard view of rolling-12 turnover belongs on the bookkeeper’s monthly review, not the year-end checklist.

Tax invoices and the A$82.50 / A$1,000 thresholds

For supplies of A$82.50 or less (including GST), no formal tax invoice is required. A receipt, cash-register docket, or any record showing the seller’s identity, the date, a description, and the GST-inclusive amount is enough to support a GST credit claim ^[4] .

For supplies of more than A$82.50 and less than A$1,000, a valid tax invoice must contain seven specified details ^[4] :

1. The document is intended to be a tax invoice (in practice, the words “Tax Invoice” prominently displayed; Peppol eInvoices automatically satisfy this requirement without the wording)
2. The seller’s identity (business name)
3. The seller’s ABN
4. The date the invoice was issued
5. A brief description of the items sold, including quantity and price where applicable
6. The GST amount payable, either shown separately or as the statement “Total price includes GST” (valid only if GST is exactly 1/11 of the total)
7. The extent to which each sale is a taxable supply (which items carry GST, which are GST-free, which are input-taxed)

For supplies of A$1,000 or more, the invoice must also identify the buyer, either by name or by ABN ^[4] . A single tax invoice covering a sale to multiple recipients must show each recipient’s name or ABN.

A supplier that is registered for GST must, on request, provide a tax invoice within 28 days ^[4] . Suppliers under the registration threshold who are not registered should issue an “Invoice” rather than a “Tax Invoice”, and the document must include the statement “No GST has been charged”.

A few practical pitfalls are common at the BAS reconciliation stage. Thermal-paper receipts fade and are easy to lose; a clear digital image preserves the audit trail. Invoices smaller than A5 or in very small font are hard to scan reliably; the ATO recommends standard A4 or A5 paper sizes. Documents that say “Tax Invoice” but also show “No GST has been charged” are internally contradictory and not valid for either treatment. ExpenseFlow surfaces all three patterns at capture.

The ABN: format, lookup, and no-ABN withholding

An Australian Business Number is an 11-digit identifier issued by the Australian Business Register ^[5] . The structure is nine digits with two leading check digits, calculated using a modulus-89 algorithm. The number is usually displayed in the format XX XXX XXX XXX (e.g. 51 824 753 556). The check-digit algorithm means a typo or OCR misread of one digit can be detected programmatically without a registry lookup.

If a supplier does not quote an ABN and the total payment for goods and services is more than A$75 (excluding GST), you generally have to withhold the top rate of tax from the payment and remit it to the ATO ^[6] . The current top rate (including the 2% Medicare levy) is 47%. Most suppliers respond to a payment-on-hold request by providing their ABN within a day; the alternative for genuinely-unregistered suppliers is the “Statement by Supplier” form.

ExpenseFlow extracts the ABN from every supplier receipt and checks the format against the 11-digit pattern and the mod-89 algorithm. A format failure is surfaced for review before the bill is posted. The live ABR registry lookup at abr.business.gov.au is an optional pre-push check that runs against contacts synced from Xero when the practice enables it on the workspace; it returns the registered name, registration status, and GST-registration status for the ABN. The live lookup is on the roadmap to ship default-on once we move past the founding cohort.

Edge cases ExpenseFlow handles at capture

Most GST errors are small, repetitive, and obvious in hindsight. They scale badly across hundreds of invoices a quarter, and the cost of catching them at the BAS is much higher than catching them when the receipt is first scanned. ExpenseFlow’s compliance engine encodes the Australian-specific rules that bookkeepers flag most often.

Alongside these deterministic rules, every captured document passes through an AI review that reads an ATO-derived knowledge base of Australian GST guidance. The review handles the judgment-heavy cases that resist fixed rules: a foreign supplier coded as if it were domestic (and the reverse, an Australian supplier coded as if it were foreign); an imported service that triggers the Division 84 reverse charge; a fixed-asset purchase posted to an expense code; an invoice whose date sits outside the claim window; a stale or implausible tax rate the engine cannot resolve to a known supply; a document addressed to a different legal entity than the practice’s client. Each finding carries an explanation and, where applicable, a suggested replacement tax code drawn from the practice’s actual platform chart. The split is intentional: thresholds, format, math, and the other rule-shaped things stay deterministic; only cases that genuinely need semantic judgment go through the AI path. The review also catches the rule-of-thumb errors that are hard to encode as fixed checks: entertainment expenses booked through the wrong account, private-use portion of a vehicle expense, claims on input-taxed supplies, and the borderline cases on the GST food list.

The combined effect is that the bill or expense arriving in Xero or QuickBooks Online is already coded, already rate-checked, and already screened against the Australian-specific edge cases. The bookkeeper’s review at month-end is the second line of defence, not the first.

GST and your accounting software

The BAS lives or dies on the integration between your receipt-capture tool and your accounting platform. The data that matters for the BAS is the tax code, the GST amount, the net and gross amounts, the supplier ABN, and the invoice date. Lose any of those during the sync and BAS reconciliation becomes a manual reconstruction project.

ExpenseFlow syncs natively with Xero (see the Xero integration page) and QuickBooks Online (see the QuickBooks Online integration page). Both syncs are two-way and continuous. Tax codes are mapped against the live tax-rate list at the platform; supplier contacts are matched against the contact cache; attachments (the captured receipt image) are uploaded so the document sits on the bill or expense in the platform. Xero tracking categories and QuickBooks classes are preserved so the management-reporting splits a practice has set up survive the sync.

A separate platform-compatibility check runs at sync time. Revenue accounts on bills, income accounts on expenses, and bank or cash accounts on invoices are all flagged so a misclick in the chart of accounts does not land an entry in the wrong ledger. The check is tuned to each platform’s conventions: Xero’s 200-299 revenue and 800-899 bank account ranges, and QuickBooks’s account-class metadata.

MYOB is on our integrations roadmap; see the MYOB roadmap page. Until the native integration ships, MYOB practices can forward receipts to ExpenseFlow’s inbound email address and the extraction pipeline runs as normal, with manual export to MYOB at the end of each period. Reckon is also on the roadmap; the same workaround applies.

For practices already on Xero or QuickBooks, the recommended workflow is to capture every receipt through ExpenseFlow (mobile photo, email forward, drag-and-drop, or batch upload), let the AI extract, code, and run the Australian compliance checks, and let the sync push the cleaned data into the accounting platform. The BAS is then constructed from that data in Xero or QuickBooks and lodged through the platform’s SBR-enabled BAS flow. ExpenseFlow does not lodge the BAS itself; the responsibility for lodgement rests with the practice and the platform that holds the BAS-lodgement credentials.

Records, retention, and the audit trail

You must keep most GST records for at least 5 years ^[10] . The retention period starts from when the record was prepared or obtained, or when the transaction completed, whichever is later. Some records have a different start date for the 5-year clock (FBT records start from the FBT-return lodgement date; super-fund-choice records start from employee engagement or the date the employee chooses a fund).

Records include sales and purchase invoices, import documents, BAS copies and supporting calculations, the tax invoices supporting GST credit claims, and documents that show the business-use portion of any expense that has private use ^[10] . The ATO accepts records kept in electronic form provided the system meets the five record-keeping rules (records cannot be altered; the system can reconstruct the original data; the records can be produced when requested; records of the system itself are kept; the system is appropriately protected).

For a practice managing BAS lodgement for multiple clients, the 5-year retention period across hundreds of clients makes paper storage impractical. ExpenseFlow stores every captured receipt at original resolution alongside the extracted data; the audit trail from source document to BAS row is preserved without paper.

A few classes of document still benefit from being kept in their original form alongside the digital workflow record. Customs declarations, the original ATO-issued correspondence, and statements from financial institutions for material loans are the most common cases.

Cross-border: imports, exports, and reverse charge

Australian GST has two cross-border patterns worth a brief note in this guide. Imported goods worth more than A$1,000 are subject to GST (and customs duty, where applicable) charged to the importer at the border by the Australian Border Force; the relevant tax code at the accounting platform is “GST on Imports” (or the platform’s equivalent). For low-value imported goods with a customs value of A$1,000 or less, GST applies from 1 July 2018 ^[9] , and the non-resident merchant or electronic distribution platform collects the GST at the point of sale and remits it to the ATO. In practice this means most online purchases from overseas sellers already arrive with Australian GST charged.

Imported services and digital products (cloud software, online subscriptions, professional services from overseas) follow a reverse-charge pattern when the supplier is not registered for Australian GST. The Australian buyer self-assesses the GST: it reports both the GST it would have paid as input GST and the GST it would have charged as output GST on the BAS, with a net effect that is typically zero. The reporting is still required and the accounting platform’s “GST on Imports” tax code handles the reverse-charge bookkeeping automatically.

Common GST mistakes bookkeepers catch

Across the Australian practices in the founding cohort, six mistakes account for the bulk of pre-BAS corrections. They are listed in roughly the order of frequency we see at capture.

Government charges coded with GST. ASIC fees, council rates, stamp duty, and motor vehicle registration are the most frequent offenders. The compliance engine flags them at the line level.

Bank fees coded as GST-on-expenses instead of input-taxed. Default behaviour in some practice templates is to code anything from a bank vendor as 10% GST. The merchant-fee carve-out makes this worse: bookkeepers correct the bank-fee coding, then over-correct and miss that the Square / Stripe / Tyro lines should stay at 10%. The engine handles both directions.

ABN missing on tax invoices over A$82.50. The supplier forgot. The receipt looks normal. Without the ABN, no GST credit is recoverable. The threshold check at capture surfaces the gap before the bill is posted.

Buyer identity missing on invoices A$1,000+. Easier to miss than the under-A$1,000 fields. The check is run at the line-total level so it catches both single-line and multi-line invoices over the threshold.

Restaurant and entertainment GST claimed in full. Business entertainment has specific FBT and GST consequences that depend on whether the entertainment is for employees or clients, whether it is provided on the business premises, and whether it is part of a fringe-benefit calculation. The AI reviewer reads the relevant ATO guidance and flags candidate violations for the bookkeeper’s call rather than auto-coding.

Mixed supplies on one invoice with no breakdown. A restaurant invoice covering both alcoholic drinks (taxable) and basic food (GST-free) but showing a single GST line at the total. Hard to fix automatically but easy to flag for review.

All six are caught at capture, before the data lands in Xero or QuickBooks. The BAS is constructed from data that has already been screened.

Where to go next

This guide is the foundation. The practical, country-specific compliance work happens on the Australia landing page, which covers ExpenseFlow’s Australian product surface end to end: BAS audit trail, integration coverage, pricing, and the specific catches the engine ships with today. The Xero integration page and the QuickBooks Online integration page cover the sync semantics for the two SBR-enabled platforms we support natively.

Pricing for Australian practices is at /pricing/bookkeepers (multi-client practice plans) and /pricing/business-owners (single-business plans), both billed in USD with tax-invoice receipts available where required.

If you are evaluating expense-capture tools for an Australian practice, the best next step is to join the founding-customer cohort with the platform you are on flagged. We onboard practices in cohorts; the first Australian cohort lands this year. The request signal is also how we prioritise the MYOB and Reckon integrations on the roadmap.