The self-lodgement tax deadline falls on 31 October every year, closing the four-month window that opened on 1 July. 31 October 2028 falls inside October, the final month of that window, in the fourth calendar quarter of 2028, with the deadline drawing closer as the month progresses.
Tuesday 31 October 2028 carries no recurring public holiday of its own outside the first Tuesday of November, when the Melbourne Cup applies in metropolitan Melbourne. On every other date, this day of the week runs as a standard working day across the country, counted fully in the working-day total above.
The quarter containing 31 October 2028 is based on the calendar year running January to December, a separate system from the Australian financial year, which runs from 1 July to 30 June and splits into its own four quarters. Businesses often track both systems side by side, one for tax filings and one for calendar-year planning.