Am I required to keep a copy of the return filed as proof and for how long?

​​​Yes, since legal proceedings under the Income-tax Act can be initiated up to four or six years (as the case may be) prior to the current financial year, you must maintain such documents at least for this period. However, in certain cases the proceedings can be initiated even after 6 years, hence, it is advised to preserve the copy of return as long as possible. Further, after introduction of the e-filing facility, it is very easy and simple to maintain the copy of return of income.​​