Hello Dear,
As per the given information on its official website The EWS certificate is valid for only one financial year from the issue date. You can check the Department of revenue website of your state to check if the validity of EWS certificate is for one year or for six months. You have to show your EWS certificate only when you qualify the exam, so at the time of document verification (after declaration of result) it should be valid.
Good Luck
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