A parliamentarian must ensure that any expenses incurred are for the ‘dominant purpose’ of conducting parliamentary business.
The ‘dominant purpose test’ governs when a parliamentarian may access public resources. Where the parliamentarian’s main reason for undertaking the activity is parliamentary business, they will have satisfied the dominant purpose test.
The test is whether the parliamentarian would have undertaken the travel or incurred the expense 'but for' the parliamentary business, which must be the 'prevailing' or 'most influential' purpose of the travel. Any personal matters during parliamentary business travel must be incidental to the trip. Expenses should not be claimed if they are for the dominant purpose of personal or commercial activities.