BAS Lodgement Due Dates and Late Penalties in Australia

The dates are the easy part. What actually causes a late BAS is rarely the calendar — it is a set of transactions the books cannot finalise because nobody has the paperwork yet.

Quarterly BAS due dates

These are the standard dates. If the due date falls on a weekend or public holiday, the BAS is due the next business day.

The December quarter is the exception. Its standard date is 28 February, which already carries the longer window because of the Christmas period, so the agent concession does not extend it further. Agent concession dates are set by the ATO's lodgment program each year — confirm the current year's dates rather than assuming they repeat exactly. *28 February 2027 falls on a Sunday, so the effective due date is the next business day, Monday 1 March 2027.

Monthly and annual lodgers

Monthly BAS is due on the 21st of the month following the reporting period. A business must report monthly if its GST turnover is $20 million or more, and some businesses elect to do so voluntarily.

Annual GST returns are generally due when the income tax return is due. If no income tax return is required, the date is 28 February following the financial year.

What a late lodgment costs

The failure to lodge on time penalty is calculated in penalty units: one unit for each period of 28 days, or part thereof, that the statement is overdue, capped at five units. That cap is then multiplied for larger entities — by two for a medium entity, and by five for a large entity.

In dollars: the penalty unit was $330 until 30 June 2026 and is indexed to $364 from 1 July 2026. A small entity that lodges a BAS three months late is looking at four units — about $1,456 — and the five-unit cap reaches $1,820 per statement. The penalty applies per statement, so four late quarters is four separate penalties, not one. Indexation changes the dollar figure periodically, so check the current unit amount on the ATO website when it matters.

Separately, any unpaid amount attracts the general interest charge, compounded daily at a rate the ATO updates each quarter. Penalty and interest are different things and can both apply at once.

Lodging on time without paying avoids the penalty entirely. This is the single most useful thing to know. If the cash is not there, lodge the statement and arrange a payment plan. The penalty is for late lodgment, not for late payment.

Getting a penalty remitted

The ATO has discretion to reduce or remove a failure to lodge penalty. In practice it is commonly remitted where the business has a good compliance history and the lateness was a one-off, or where something genuinely outside the business's control intervened — illness, a natural disaster, a failure by a third party.

Remission is not automatic. It has to be requested, with an explanation of what happened and what has changed so it does not recur. A request that also demonstrates the overdue statements are now lodged carries considerably more weight.

Why BAS deadlines actually get missed

Across bookkeeping practices, late BAS lodgments follow a small number of predictable patterns, and none of them are about forgetting the date.

The GST position is not final. A batch of purchases has GST coded but no tax invoice attached. Claiming those credits without holding the invoice is not an option, and excluding them means an amended figure later. So the file waits.

The client responds in the last week. Requests for missing paperwork go out individually over the quarter, get missed in an inbox, and the real chase starts when the deadline is close enough to be alarming.

Nobody knows the size of the gap. Accounting software will not tell you which transactions lack a source document, so the shortfall is discovered during preparation rather than weeks beforehand.

The chase has no record. When three people have asked the same client for the same receipt by email, text and phone, nobody can tell what is still outstanding.

A routine that keeps lodgment on time

The aim is to arrive at the due date with nothing outstanding, which means treating the paperwork deadline as several weeks earlier than the lodgment deadline.

1. Six weeks out. List every transaction with GST coded and no document attached. Sort by GST amount — that total is the exposure if the quarter closes as is.
2. Five weeks out. Send the client one consolidated request covering every missing item, not a series of separate emails.
3. Three weeks out. Follow up on what is still outstanding, and flag anything material that may need its credit excluded.
4. Two weeks out. Attach everything received to its transaction, and mark items that legitimately have no invoice — bank fees, interest, internal transfers — so they are not re-examined next quarter.
5. One week out. Finalise, review the GST reconciliation, and lodge. Anything above $82.50 including GST that is still unsupported has its credit excluded rather than claimed on faith.

For the substantiation rules behind that last step, see how to substantiate GST credits in Australia, and for what counts as a valid invoice, see tax invoice requirements in Australia. For finding the unsupported transactions in the first place, see how to find bills without receipts attached in Xero.

Frequently asked questions

This article is general information and is not tax advice. Due dates, penalty unit values and interest rates change. Confirm anything material with a registered tax or BAS agent, or with the ATO.