Depreciation

Let it be internal audit or whatever, EXCEPT FOR COMPANIES, for all other assessees, depreciation rates as per Income Tax Act are followed. And for Companies, dual exercise you will have to do. First, while preparing Bal Sheet and P&L A/c. and Schedules etc follow Companies Act rates and while filing ITR and while preparing Tax Audit Report, Income Computation etc follow I Tax rates.

Theoretical concept - if assessee has any other suitable base for depreciation calculation, he can follow that provided if it results in proper presentation of books of accounts etc etc. In practical, except some major identical big companies, no one goes for it.