Written down value rules preserve asset base and carryover on specified transfers and reorganisations under income-tax law. The provision defines written down value for computing business income, distinguishing assets acquired in the tax year, assets acquired earlier, and blocks of assets calculated by a formula reflecting prior block value, additions, disposals (capped), and depreciation actually allowed; it deems depreciation carryforwards as depreciation actually allowed. Specific corporate events-holding-subsidiary transfers, amalgamation, demerger, conversion to limited liability partnership, corporatisation transfers, and succession-preserve or fix written down value or actual cost in the hands of the transferee or resulting entity corresponding to the transferor's immediately preceding tax-year position, with adjustments for revaluations and book depreciation where the assessee did not compute prior-year income.