Behind on BAS: A Sydney Bookkeeper's Step-by-Step Catch-Up

Updated: November 2026

For hands-on help with this, see books catch-up Sydney.

If you have several BAS overdue, the catch-up plan is the same every time: list what is missing, reconcile and lodge the oldest quarter first, keep going until every statement is in, then deal with the debt. Lodge even if you cannot pay, because each late BAS has its own failure to lodge penalty and lodging stops it growing. Most businesses can be back up to date within weeks once the records are found. This guide sets out each step in order. If only one quarter is late, our shorter guide on being behind on BAS may be all you need.

Why does it matter how many quarters are overdue?

Each BAS is a separate lodgement with its own penalty clock:

The failure to lodge penalty is one penalty unit for each 28 days or part late, up to 5 units, per statement. From 1 July 2026 a penalty unit is $364, so one BAS more than 112 days late could reach the 5 unit maximum of $1,820 for a small business.
Three overdue quarters means three penalties, each calculated separately.
Unpaid amounts attract the general interest charge, which is 11.51% a year for October to December 2026, compounding daily, and not deductible from 1 July 2025.
Agent lodgment program concessions generally need the previous statement to have been lodged electronically, so catching up quickly helps you keep the extra weeks for later quarters.

Step 1: What exactly is overdue?

Log into ATO Online services for business and list every outstanding activity statement.
Note any IAS, PAYG instalments or STP finalisation that are also outstanding.
Download your ATO account statement to see what has already been charged.
Open any ATO letters. They often show deadlines or offers you need to respond to.

Step 2: Is the Xero file usable?

Check the state of your books for each overdue quarter. If bank accounts are reconciled and receipts are attached, preparing the BAS is quick. If not, the file needs to be reconciled before any BAS can be trusted. Our books catch-up service handles this on a fixed quote, and our guide to a messy Xero file explains what is involved.

Step 3: Reconcile and lodge the oldest quarter first

Start with the oldest quarter, because later quarters depend on correct opening balances.
Reconcile every bank account, match bills and receipts, and check GST coding.
Run a GST reconciliation, prepare the BAS, review it with you, and lodge.
Move to the next quarter and repeat.
Remember GST credits generally need to be claimed within 4 years, so very old missing receipts are worth chasing now.

Step 4: Talk to the ATO early

The ATO generally responds better to businesses that engage. A registered agent can speak to the ATO for you, confirm what is outstanding and discuss timeframes. If penalties have been applied, you can ask the ATO to consider remission, explaining what happened and what you have changed.

Step 5: Deal with the debt

Once everything is lodged, total the amount owing.
If you owe $200,000 or less and meet the criteria, you may be able to set up a payment plan online.
GIC keeps accruing on the balance under a payment plan, so pay what you can upfront.
Treat the debt like a loan: compare the GIC rate with other ways of funding it, and ask your accountant for advice.

Our article on what a late BAS costs in 2026-27 covers the figures in detail.

Step 6: Stay current from now on

Reconcile weekly, so the next BAS is ready before it is due.
Set aside GST each week in a separate account.
Use a registered BAS agent to lodge, and check your own ATO account after each due date.
Pay super each payday under Payday Super, so a BAS catch-up does not turn into a super catch-up as well.

Our BAS lodgement service and monthly bookkeeping keep you on schedule.

How long does a catch-up take?

It depends on how many quarters are overdue and the state of your records. A few quarters with bank feeds connected can often be done in weeks. Missing statements, cash transactions or no receipt capture take longer. A fixed quote, scoped after looking at the file, tells you the cost before anyone starts.

What do most people miss?

Avoiding the ATO makes it worse. Every month of delay adds penalty and interest, and an unlodged BAS can lead the ATO to estimate what you owe. Lodging, even with a debt you cannot pay yet, puts you back in control.

What records will you need for the catch-up?

Bank and card statements for every overdue quarter.
Sales records, such as invoices, POS reports or platform payouts.
Supplier bills and receipts, especially for larger purchases.
Payroll records, including pay runs, STP reports and super payments.
Loan, hire purchase and asset purchase documents.
Any ATO letters or notices received.

Missing receipts do not stop the catch-up. The BAS can still be lodged, but GST credits need a valid tax invoice for purchases over $82.50, so finding the larger ones is worth the effort. Suppliers can usually resend invoices if you ask.

What should you say when you contact the ATO?

Keep it simple and truthful. Explain which statements are outstanding, that you have engaged a registered agent, and when you expect each one to be lodged. Then meet those dates. If you cannot pay in full, say so and ask about a payment plan. Write down the date, the name of the person you spoke to and any reference number, so you have a record if questions come up later.

Once the catch-up is finished, set a reminder to check the ATO portal after each due date for the next year. A few quick checks confirm the new routine is working and give you confidence that you will not fall behind again.

FAQ

Should I lodge my BAS if I cannot pay?

Yes. Lodging stops the failure to lodge penalty growing. Then arrange payment or a payment plan.

Which BAS should I lodge first?

Usually the oldest, because each quarter's opening balances depend on the one before.

Can the ATO waive penalties on late BAS?

The ATO can remit penalties in some circumstances. A clear explanation and evidence that you have fixed the cause helps.

How much does a BAS catch-up cost?

It depends on the number of quarters and the state of the file. We quote a fixed price after reviewing your records.

Several quarters behind?

We reconcile, lodge oldest first and talk to the ATO for you, on a fixed quote agreed before we start.

Next step: send us a message and a real person replies within a few working hours, or book a free Xero Roast, a 15-minute plain-English review of your file with a fixed quote at the end. Our fixed monthly packs include a 4-hour reply guarantee, no lock-in and a 30-day money-back guarantee.

About Sydney Bookkeeper

Sydney Bookkeeper is the modern, fixed-price Sydney bookkeeper for businesses with staff that are tired of slow, hourly, jargon-spouting incumbents. We work with professional services firms, construction and property businesses, agencies, tech and ecommerce companies, hospitality groups, and health practices across Sydney. Monthly bookkeeping, BAS lodgement, payroll, and Xero file cleanups, all on fixed monthly pricing, no lock-in.

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The team uses a registered BAS Agent for all BAS and IAS lodgement services. Full registration details, agent particulars, and copies of the Tax Practitioners Board (TPB) Code of Professional Conduct, the TPB complaints process, and any conditions on the agent's registration are available on request by emailing hello@sydneybookkeeper.com. This content is general information only, written for Australian small and mid-market businesses. It does not constitute tax, financial product, or legal advice and should not be relied on as such. Tax obligations depend on your individual circumstances. For advice specific to your business, contact the team directly or consult a registered tax agent or licensed financial adviser. Sydney Bookkeeper is not a licensed tax agent or licensed financial adviser. Information was current at the time of publication and may change without notice. We review and update guides periodically.

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