When will expire unused salesforce certification voucher which got in July 2023??

HI @Akhilesh Burungale

In most cases, certification vouchers have a specific expiration date by which you must schedule and complete your exam. If you schedule your exam before the voucher expiration date but the actual exam date is after the voucher expiration date, it may or may not be allowed. 

I recommend reaching out to Salesforce's certification support or the webassessor certification authority. They will be able to provide you with the specific details and policies regarding scheduling exams with voucher expiration dates