Depreciation recalculation: companies must recompute specified period and adjust straight-line charges after tax-rate changes per statutory guidance. Companies using the straight line method must recalculate the specified period under revised income-tax depreciation rates by: identifying years already depreciated, computing the specified period under revised rates by which the prescribed residual of original cost is depleted on written down value basis, noting written down value at the rate-change year start, and residual value. Thereafter, fixed annual instalments equal (written down value minus residual value) divided by remaining recalculated years must be charged; if years already depreciated exceed the recalculated period, the balance may be provided as depreciation in the year of change.