Applicability of IND AS

Dear Experts, 

As all of you know that, INDAS is applicable to the selective classes of companies and other companies can adopt the same is as per their discretion. I have a query in this;

Whether this INDAS is only applicable for the preparation of financial results. If a company is keeping it's books of accounts in IGAP and at the year-end, the COmpany is converting those figures to as per INDAS for the preparation of financial reports.Whether this practice is legally valid or not?

Thanks in advance