Australian Financial Year (AU FY) week numbering counts weeks against the Australian financial year, which runs 1 July to 30 June. Week 1 begins on 1 July, regardless of day of week, and every subsequent week begins exactly 7 days later, through to week 52 or 53 on 30 June.
What is the Australian Financial Year?
The Australian financial year runs from 1 July to 30 June. The current financial year, on 28 May 2026, is FY2025-26, which began on 1 July 2025 and ends 30 June 2026. FY2026-27 starts on 1 July 2026.
The Income Tax Assessment Act 1936 (section 6) and the Income Tax Assessment Act 1997 set the financial-year-as-tax-year convention. The Australian Taxation Office administers it; see https://www.ato.gov.au/ for primary guidance.
The 1 July start was inherited from UK Treasury practice but shifted earlier in the calendar. The United Kingdom uses 6 April for individuals and 1 April for corporates; Australia chose 1 July.
ATO reports, Business Activity Statement (BAS) submissions, PAYG payroll cycles, and almost all small and medium business accounting in Australia use this boundary.
How AU FY week numbering works
Week 1 begins on 1 July, whatever day of the week that falls on. Week 2 begins 7 days later. Every week boundary is a fixed 7-day offset from 1 July. There is no Monday alignment. This differs from ISO 8601, which always starts week 1 on a Monday. FY2025-26 week 1 starts on Tuesday 1 July 2025; week 2 starts on Tuesday 8 July 2025.
The calculator on the home page applies this rule automatically when you select the Australian Financial Year mode. The step-by-step algorithm and code samples sit on a separate page.
Examples
Three concrete cases show the AU FY week rule at work.
- 1 July 2025 (Tuesday) → AU FY2025-26, week 1. Day 0 from the 1 July anchor.
- 28 May 2026 (Thursday) → AU FY2025-26, week 48. 329 days from 1 July 2025.
- 30 June 2026 (Tuesday) → AU FY2025-26, week 53. The last day of the financial year.
When AU FY weeks matter
Several reporting and payroll situations require AU FY week alignment.
- BAS quarterly lodgement. The ATO sets four BAS quarters per financial year. Q1 covers 1 July to 30 September, due 28 October. Q2 covers 1 October to 31 December, due 28 February the following year (extended for the holiday period). Q3 covers 1 January to 31 March, due 28 April. Q4 covers 1 April to 30 June, due 28 July.
- Payroll cycles. Many Australian employers run weekly or fortnightly pay aligned to the AU FY for PAYG withholding totals and payment summaries.
- End-of-financial-year reporting. EOFY closes books at 30 June, so week-level rollups must respect that boundary.
- Superannuation contribution caps. Concessional and non-concessional caps reset on 1 July, so week 1 marks a fresh cap for each member.
- Fringe Benefits Tax (FBT) year. Caveat: the FBT year runs 1 April to 31 March, not the standard AU FY. Treat FBT separately when scheduling weeks.
AU FY vs calendar year
The AU FY and the calendar year cover the same 12 months but start six months apart, so the same calendar month sits in a different quarter under each scheme. October sits in Q4 of the calendar year but Q2 of the AU FY. January sits in Q1 of the calendar year but Q3 of the AU FY. Mixing the two schemes inside one report causes silent reconciliation errors at quarter-end.
Related terms
Compare with other standards
ISO 8601 Week Numbering anchors week 1 to the first Thursday of January and runs against the calendar year. It is the right default for international software and cross-border data exchange.
US Week Numbering anchors week 1 to the week containing 1 January and uses Sunday-start weeks. It dominates US payroll and US retail calendars but does not align with the Australian financial year.
The US federal fiscal year (1 October to 30 September) and the UK financial year (6 April to 5 April for individuals; 1 April to 31 March for corporates) differ from the Australian 1 July anchor.
FAQ
When does the Australian financial year start? The Australian financial year starts on 1 July and ends 30 June the following calendar year. The Income Tax Assessment Acts set this boundary, and the Australian Taxation Office administers it.
What is week 1 of the Australian financial year? Week 1 begins on 1 July, whatever day of the week that is. For FY2025-26 week 1 starts Tuesday 1 July 2025. For FY2026-27 week 1 starts Wednesday 1 July 2026.
How does AU FY differ from the US fiscal year? The Australian financial year runs 1 July to 30 June. The US federal fiscal year runs 1 October to 30 September. The two schemes share no quarter boundaries, so week numbers between them never match.
Do the ATO BAS quarters align with AU FY weeks? Yes. BAS quarters split the AU FY into four 13-week blocks: Q1 weeks 1-13, Q2 weeks 14-26, Q3 weeks 27-39, and Q4 weeks 40-52 or 53. Each quarter ends on a fixed calendar date.
For the step-by-step algorithm and worked examples, see How Australian Financial Year Week Numbers Are Calculated.
Articles in this section
- How Australian Financial Year Week Numbers Are Calculated — How to calculate week numbers under the Australian financial year (1 July – 30 June), with worked examples and BAS-quarter alignment.