Depreciation and amortisation rules require systematic allocation by useful life and assignment to cost objects under clear disclosure norms. Principles require systematic allocation of an asset's depreciable amount over its useful life, with key concepts defined for depreciable amount, residual value and useful life. Measurement must reflect the consumption pattern of economic benefits and may use methods such as straight line or units of production. Minimum depreciation must comply with applicable law or regulator prescriptions; revaluation impacts and impairment losses are excluded from cost assignment. Depreciation is assigned to cost objects by tracing or by cause and effect or benefits received apportionment and, if material, must be separately presented and disclosed in cost statements.