Review transactions around your GST registration date

This guide starts after the registration decision. If you haven't yet worked out whether registration is required, read how to register for GST first. For the first business activity statement (BAS), give transactions that straddle the start date their own review.

Confirm the effective date in the registration record

Use the ATO confirmation, not the day someone changed the invoice template. Record the entity, ABN, effective GST date, reporting cycle and GST accounting basis. If a registration was backdated, keep that confirmation and the reason for the change.

The ATO registration guidance explains that a business required to register can owe GST from when registration was required, even if it did not charge customers GST. Backdating can affect sales and purchase credits together; it isn't a way to select only favourable transactions.

Make a timeline before changing tax codes

The fictional example below uses an effective date of 1 September. It deliberately leaves treatment decisions open where the facts matter. Receiving money after 1 September doesn't establish that it relates to a taxable post-registration supply.

Before registration

20 August: equipment purchased. 25 August: service invoiced. Save the purchase document, service period and contracting entity.

Effective date: 1 September

GST registration starts for the named entity. Preserve the confirmation and software settings.

After registration

5 September: old invoice paid. 12 September: new work invoiced. 18 September: stock bill received. Link each date to its actual supply and payment evidence.

Read each transaction on its own facts. The date line does not assign GST automatically. Original ASBG diagram with a complete text equivalent in each step; fictional examples.

Transaction	Documents	Question for review
Receipt for pre-start work	Contract, service dates, invoice and payment	Was the supply made before registration was required, and what attribution applies?
Earlier equipment purchase	Invoice, purchase date, use and ownership	Was the business registered or required to be registered; does any specific entitlement apply?
Trading stock held at the start	Stocktake, invoices and earlier claims	Does a specific stock-on-hand provision apply, and how is the amount worked out?
Company setup costs paid by founder	Formation date, payer, invoices and reimbursement	Are the pre-establishment criteria all satisfied?

This is a preparation checklist. None of these rows creates a credit merely because the business is now registered. Original ASBG worksheet; all example figures are fictional.

Don't apply one rule to every earlier purchase

Pre-registration stock, earlier equipment, private purchases brought into a business and costs incurred to establish a company are different situations. Keep them separate. A purchase before the business existed can also involve a different purchaser from the entity now lodging the BAS.

The ATO's GST guide discusses specific credit rules and company pre-establishment costs. For the company concession, criteria include when the company came into existence and registered, who incurred the cost, the connection to the company and reimbursement. Ask the agent to record which provision applies; don't assume "bought for the business" is sufficient.

Review invoices that customers haven't paid

Export open customer invoices and supplier bills at the effective date. Add any payments already made, including deposits. GST attribution depends on the facts and cash or non-cash accounting rules; changing a report setting doesn't rewrite the underlying transactions.

Where an old invoice needs correction, retain both versions and explain why. Check the contract before assuming you can add GST to an agreed price. An entity change needs further care: an old sole trader invoice should not simply be moved into a new company's reporting.

Finish with a documented first-BAS check

For each exception, record the agent's conclusion, GST amount, reporting period, source and any follow-up action. Confirm the normal invoice template and supplier tax codes apply from the approved dates. Keep unresolved items on a list rather than hiding them in a general expense account.

Save the first BAS and transaction report alongside this transition schedule. Next quarter, check that old receipts or late supplier paperwork haven't reintroduced the same issue. The BAS foundation guide explains the ongoing cycle.

Continue with the next question

• Cash or accrual GST accounting: compare the timing
• Missing tax invoice? Check the evidence before claiming GST

Key takeaways

• Use the confirmed effective date and the correct entity.
• Separate supply, invoice, purchase and payment dates.
• Review earlier stock, assets and setup costs under their specific rules.

Where to get help

Have a registered tax or BAS agent review the first-period schedule. Use the ATO registration page for registration rules and Bookkeeping and BAS for the records needed afterwards.