Nil TDS Returns are mandatory

NO , NOT REQUIRED 

If had no TDS liability during any Quarter than you need not to TDS Return.

It is not mandatory to file nil TDS return if you have not deduct TDS for any quarter.

However you have to file a declaration for non filing of TDS Return. 

The Deptt. has introduced a new functionality in the TRACES site wherein the persons who are not required to submit a return of TDS due to non applicability in any particular quarter shall have to submit a Declaration for the same on TRACES. Procedure for filing of Nil TDS return/ declaration for non filing of TDS statement is given below: 

1. Login through your registered id at www.tdscpc.gov.in (TRACES site) 

2. Go to Statement/Payments TAB after login > Declaration for Non filing of TDS statement