5e737bcd_siness_and_Professional_Income__Current_expenses
[Criteria] Is the expense for a part of a property or for a separate asset? [Capital expenses] The cost of replacing a separate asset within a property is a capital expense. For example, the cost of buying a compressor to use in your business operation is a capital expense. The reason is that a compressor is a separate asset and is not part of the building. [Current expenses] 
The cost of repairing a property by replacing one of its parts is usually a current expense. For instance, electrical wiring is part of a building. Therefore, an amount you spend to rewire is usually a current expense, as long as the rewiring does not improve the property beyond its original condition.
T4002 - Business and Professional Income
Current expenses