well, one thing should be distinctly understood.
1. The depreciation for the purpose of Income tax is to be computed as per income tax Act only, thus
whether the taxable entity is company or not, it is to be followed.
2. The depreciation for the purpose of company is to be applied as per SCH VI which stipulates rate as minimum rate of depn. So companies are at freedom to charge higher rate of deprn provided it gives a true and fair view.
thus for income tax 15 p.c. will be considered irrespective of rate as per sch VI