Depreciation limits restrict block-wise allowance and adjust written down value for assessees opting into concessional tax regimes. Depreciation rules require calculating allowance on a block of assets at percentages specified in Appendices I and IA, applied respectively to written down value and actual cost; aggregate depreciation cannot exceed actual cost where applicable. Taxpayers may elect between methods, with the election being final once timely made. Certain taxpayers opting into concessional tax regimes face a cap on block-wise depreciation, and transitional provisions mandate increasing written down value on prescribed dates by prior-year depreciation or unabsorbed depreciation not set off, subject to specified conditions. Special qualifying treatment applies to plant using laboratory-developed technology with certification.