Yes if you are not in central obc list then you can apply for ews. Check obc central list at www.ncbc .nic. in

Nikita, Jaats fall under OBC Category. And EWS reservation is for those Candidates who belong to General Category and whose annual income from all sources is less than 8 lakhs per annum. But as you belong to OBC, you are not eligible for EWS reservation.

As per my knowledge, Jaats don't come under General category. If it is so, then you are not eligible to apply for EWS Certificate because in that case you will already be taking the benefit of reservation on the basis of your caste.

If it is not so and you are the candidate of General category, then you are eligible to apply for EWS certificate, provided that you satisfy all the required conditions like, Income, Land, etc.