Australian tax deadlines: BAS, income tax, and super due dates

Australia’s small business tax calendar pivots on the BAS cycle, and in 2026 it gains its biggest change in years: payday super. From 1 July 2026, super stops being a quarterly obligation and becomes part of every pay run ^[3] . Here are the dates an Australian SMB and its bookkeeper live by, each verified against the ATO sources in the Sources section.

The quarterly BAS dates

For businesses with GST turnover under $20 million (the default quarterly cycle) ^[1] :

Three wrinkles worth knowing ^[1] :

• Q2 gets no further extension: the 28 February date already includes a built-in extra month for the holiday period.
• Lodging online can add up to 2 extra weeks to the other quarters, and registered tax or BAS agents get extra time under their lodgment program.
• Weekend rule is generous: if the due date falls on a weekend or public holiday, you have until the next business day.

Monthly lodgers (compulsory at $20 million GST turnover or more, optional below) report by the 21st of the following month ^[1] . Voluntarily registered businesses under $75,000 turnover ($150,000 for not-for-profits) can report GST annually ^[1] .

Income tax lodgment

Self-lodged individual returns, including sole traders, are due 31 October for the income year ended 30 June ^[2] . Lodging through a registered tax agent usually unlocks later dates under the agent lodgment program, stretching well into the following calendar year, provided the client is on the agent’s list before 31 October ^[2] . Company return dates vary by entity history and size under the same program; the date assigned shows in ATO online services.

Payday super: the July 2026 reset

The Treasury Laws Amendment (Payday Superannuation) Act 2025 is law, and the start date held: 1 July 2026 ^[3] . From that date:

• Super guarantee (12% of qualifying earnings) is payable every payday, not quarterly ^[3] .
• The super guarantee charge applies when contributions have not been received by the fund within 7 business days of payday (with limited exceptions, such as new employees) ^[3] .

For weekly payrolls this multiplies super payment events by roughly 13. The bookkeeping consequence is blunt: super liabilities must be calculated, paid, and reconciled inside the pay cycle, which only works if payroll and the ledger agree continuously rather than at quarter end.

The employer year-end stack

After 14 July, employees see “tax ready” income statements in myGov, which is when individual return season effectively opens.

If a date slips

The ATO applies failure-to-lodge penalties that scale with how late the lodgment is and the size of the entity, and charges general interest on late payments. Two mitigations are worth knowing before the deadline rather than after. First, lodging through a registered tax or BAS agent both extends many due dates and tends to soften the penalty conversation. Second, the ATO consistently says to contact them before the due date if you cannot lodge or pay on time ^[1] ; payment plans arranged in advance are routine, while silence converts a cash-flow problem into a compliance problem. For super guarantee specifically there is no soft option: missing the deadline triggers the super guarantee charge, which is not tax deductible and includes interest and an administration component, which is exactly why payday super readiness matters before 1 July 2026.

Keeping the dates hittable

Every date above is a downstream deadline on the same upstream asset: books that are current. A BAS prepared from a shoebox takes days; a BAS prepared from a reconciled ledger takes an hour. ExpenseFlow works on the upstream side: receipts, supplier invoices, and bills are captured when they happen, coded with the right GST treatment, and synced into Xero or QuickBooks Online with the source document attached. When the 28th arrives, the quarter’s expenses are already in the ledger and evidenced. Lodgment itself stays where it belongs, in the accounting platform or with the BAS agent.