Commonwealth Numbered Acts

INCOME TAX ASSESSMENT ACT 1997 No. 38 of 1997 - SECT 900.20

You need to keep travel records if your expense is for travel that involves
you being away from your ordinary residence for 6 or more nights in a row.

The travel may be within or outside Australia. Subdivision 900-F tells you
about travel records. Note: Members of international flight crews may be
exempt from keeping travel records for losses or outgoings covered by travel
allowances: see section 900- 65.