DEPRECIATION AS PER INCOME TAX OR AS PER ACCOUNTING

SUPPOSE MR. X IS NOT CHARGING DEPRECIATION ON THEIR BOOKS OF ACCOUNTS BUT THEY WERE CHARGING DEPRECIATON AS PER INCOME TAX ACT FOR LAST TWO YEARS BUT NOW MR. X WANTS TO CHARGE DEPRECIATION ON THEIR BOOKS OF ACCOUNTS 

Q1)  WHETHER DEP. NEEDS TO BE CHARGE ON WDV OR BOOK VALUE

Q2)  MISMATCH BETWEEN UNABSORBED DEP. AS PER INCOME TAX AND BOOKS.