The self-lodgement tax deadline falls on 31 October every year, closing the four-month window that opened on 1 July. 18 October 2027 falls inside October, the final month of that window, in the fourth calendar quarter of 2027, with the deadline drawing closer as the month progresses.
The week containing Monday 18 October 2027 is counted from this date under the standard week-numbering convention used on this page, with weeks running Monday to Sunday rather than Sunday to Saturday. This convention affects rostering, payroll cycles and any planning done in weekly blocks across Australian workplaces that pay staff or schedule shifts on a weekly basis.
The working-day count on this page excludes both weekend days and any public holiday declared for the state selected, so the same date in 2027 can show a different total depending on which state's calendar applies to 18 October. Interstate businesses need to check more than one state's list before setting a national deadline.