Every employer has to maintain the contribution card in respect of each employee in Form 3A (it is in the form of a register, and a page is allotted to each employee who contributes to the Provident Fund, etc.) and submit the annual returns in Form 3A and 6A after reconciliation with Challans and Form 12A. If no such contribution was made (highly unlikely, unless the company remained closed during the year with no employees on rolls), only then a "NIL" Return is possible.