You can pay the March 2017 contribution before the due date, i.e., 21-04-2017. For the previous months, you have to file in the respective months. After the belated receipt of payment, ESIC will revert to you with a claim for interest and penalty. Since you have not paid the ESI contribution for the past 11 months, all employees will not be eligible to get the benefits provided therein. It is better to pay monthly contributions before the due date. Otherwise, in the case of employment injury/death, etc., you as the employer have to pay the benefits to the employee concerned.