Operating expenditure rules define allowable business expenses, exclusions and timing conditions for claiming deductions. The clause defines operating expenditure as the aggregate of specified allowable expenses incurred wholly and exclusively for business and defined deductions subject to conditions. It lists a wide range of permitted costs-supplies, rent, repairs, employee remuneration, insurance, selling and professional expenses, R&D, contributions to prescribed funds, certain head office and asset transfer costs-and prescribes exclusions for personal, capital, finance and prohibited items. Timing rules permit deduction when liability arises if paid by the return due date, otherwise when actually paid.