04 April 2018
Compulsory. ICDS shall apply for computation of taxable income under thehead Profit and gains of business or profession” or “Income from othersources” under the Income Tax Act. This is irrespective of theaccounting standards adopted by companies i.e. either AccountingStandards or Ind-AS.
05 April 2018
ICDS & AS are two separate standards. ICDS applicable while we calculate taxable income while AS is set of rules for accounting. So while you are accounting you have to follow AS but while you are working on taxable income you have to use ICDS.
Both are not interchangeable. So you can't adopt AS in place of ICDS.