ABN and GST registration for residential builders

TL;DR

You need an ABN before you invoice anyone. Registration is free at abr.gov.au and is usually instant online. GST registration is compulsory once your annual turnover hits $75,000: you have 21 days from the date you cross the threshold to register, or backdating and penalties follow. Once registered, you collect and remit 1/11th of every GST-inclusive invoice via quarterly BAS. The single most expensive admin mistake: a subbie on your site invoices without an ABN on their tax invoice. You are legally required to withhold 47% of that payment and remit it to the ATO before the subbie sees a dollar.

What it is

An ABN (Australian Business Number) is the unique 11-digit identifier that tells the ATO and your clients you are operating a business. It goes on every quote, invoice, and contract. Without it you cannot legally invoice for construction work, open a business bank account, or register for GST.

GST (Goods and Services Tax) is a 10% broad-based consumption tax collected by GST-registered businesses on behalf of the ATO. Residential builders and trades above the $75,000 turnover threshold are required to be registered, collect GST on their invoices, and remit it quarterly via the Business Activity Statement (BAS).

Getting your ABN

Registration is free via the Australian Business Register at abr.gov.au, or through the combined Business Registration Service at register.business.gov.au (verified 2026-05-10). You can apply for an ABN, register a business name, and register for GST in the same session.

What you need:

Tax file number (TFN) for sole traders and partners; company ACN for Pty Ltds
Details of your business structure (sole trader, partnership, company, trust)
Reason you’re entitled to an ABN (carrying on a business in Australia)

Processing time: Instant in most cases if all information matches ATO records. Manual review takes up to 28 days if information cannot be automatically verified.

Entitlement: Not everyone gets an ABN. You need to be carrying on an enterprise in Australia. Employees cannot hold an ABN for the work they do as an employee, which is the core test in sham contracting disputes (see sham contracting).

GST registration

Compulsory threshold

You must register for GST when your annual GST turnover reaches or exceeds $75,000. Non-profit bodies have a higher threshold of $150,000 (verified 2026-05-10, ATO: Registering for GST).

Annual GST turnover is your total business income (not profit) for the current month and previous 11 months combined.

You must register within 21 days of the date you first cross the threshold. If you don’t, the ATO can backdate your registration and require you to remit GST on all sales made since the date you should have registered, even if you didn’t collect it from your clients. Penalties and interest apply on top.

Voluntary registration

You can register voluntarily if you’re under the $75,000 threshold. Useful if your clients are mainly GST-registered businesses (they can claim your GST back as a credit). Once registered, you must lodge a BAS and collect and remit GST on all taxable supplies.

What registration means in practice

Obligation	Detail
Collect GST	Add 10% to the price of taxable supplies, or quote GST-inclusive
Remit GST	Pay 1/11th of GST-inclusive revenue to the ATO via BAS
Claim GST credits	Claim back GST on business purchases (materials, plant, tools)
Issue tax invoices	Required for sales over $82.50 (GST-inclusive)
Lodge BAS	Quarterly for most small builders; see below

Business Activity Statement (BAS)

The BAS is how you report and pay GST, PAYG withholding, and other tax obligations to the ATO.

Lodgement frequency

Frequency	When it applies
Quarterly	Default for most builders. Annual GST turnover under $20 million.
Monthly	Annual GST turnover $20 million or more, or if you elect monthly.
Annually	Only if you’re voluntarily registered and turnover is under $75,000.

(Verified 2026-05-10, ATO: Options for reporting and paying GST)

Most residential builders lodge quarterly. BAS quarters align with the calendar: July-September (due 28 October), October-December (due 28 February), January-March (due 28 April), April-June (due 28 July). A registered tax agent or BAS agent gets extended due dates.

What goes on a BAS

GST collected on sales (1A)
GST credits on purchases (1B)
PAYG withholding from employees’ wages (W2)
PAYG withholding from contractors who did not quote an ABN (W3)
Instalment income (if using the PAYG instalment system)

Tax invoice requirements

A tax invoice is the document that lets your client claim back the GST they paid you as a credit. You must issue one for any GST-inclusive sale over $82.50. Non-GST-registered businesses issue a standard invoice (no GST, no “tax invoice” label).

Required fields

Sale amount	Required fields
Under $1,000 (GST-inclusive)	“Tax invoice” label; your ABN; date issued; description of goods or services; GST amount, or statement “Total price includes GST”; seller’s identity
$1,000 or more (GST-inclusive)	All of the above, plus the buyer’s identity or ABN

(Verified 2026-05-10, ATO: Tax invoices)

Common mistakes builders make on invoices:

Missing the “Tax invoice” label (makes the document a standard invoice, client cannot claim GST credit)
No ABN on the invoice (triggers withholding obligation on the payer)
Showing GST separately but getting the split wrong (GST = total price divided by 11, not 10% of ex-GST price)
Progress claim invoices without a date (BAS period becomes ambiguous)

The 47% no-ABN rule: what it means for you as a principal

When you engage a subcontractor and they send you an invoice without an ABN, you are legally required to withhold 47% of the payment and remit it to the ATO before paying the subbie the net balance. This applies to any payment over $75 ex-GST (verified 2026-05-10, ATO: Withholding if ABN not provided).

The 47% rate matches the top personal income tax rate plus Medicare levy. It is not a penalty: the ATO holds it as a credit against the supplier’s tax liability. But in practice it means you pay roughly half of the invoice and the subbie is left chasing the ATO for a refund at tax time.

As the principal builder, your withholding obligations:

Withhold 47% from the no-ABN invoice amount
Pay the net amount to the subcontractor
Report and remit the withheld amount via W3 on your BAS
Issue the subcontractor a payment summary showing the amount withheld

Legitimate exceptions: The subcontractor can provide a Statement by a supplier (ATO form) declaring they are not required to have an ABN (e.g. they are an individual earning less than $75 on a one-off basis). This is uncommon in construction; most subbies should have an ABN.

For subbies on your own build: Before you let anyone on site, confirm their ABN via ABN Lookup and keep a record. Expired or cancelled ABNs are common after a business collapses.

What can go wrong

Issue	Consequence
Cross the $75,000 threshold without registering	ATO backdates registration, remit GST on past sales you never collected, plus interest and penalties
Invoice without an ABN	Payer must withhold 47%; you receive roughly half and chase the ATO at tax time
Issue a “tax invoice” when not GST-registered	Illegal. Client may fraudulently claim a GST credit that wasn’t collected.
Fail to register within 21 days of threshold	Penalty units under Taxation Administration Act 1953; amount varies
Lodge BAS late	General interest charge (GIC) applies from the due date; ATO may issue a default assessment
Miss a GST credit claim	4-year time limit to claim GST credits. Unclaimed credits are lost.
Forget to extend BAS lodgement with a tax agent	Lose extended due dates; standard dates apply

References

Australian Business Register: Applying for an ABN (verified 2026-05-10)
ATO: Registering for GST (verified 2026-05-10)
ATO: Tax invoices (verified 2026-05-10)
ATO: Withholding if ABN not provided (verified 2026-05-10)
ATO: Options for reporting and paying GST (verified 2026-05-10)
A New Tax System (Goods and Services Tax) Act 1999 (Cth) (verified 2026-05-10)
A New Tax System (Australian Business Number) Act 1999 (Cth) (verified 2026-05-10)
Australian Taxation Office