Services Tax Matter 26 AS vs ST 3 Return Difference

Hi team

I need your help. My one of client received services tax show cause notice in aug 2019 by email.for the F Y 13 14 and FY 14 -15 on basis of 26AS and ST 3 return difference.
This email was received on constultant email not received on client email.

Client has not reply to notices nor submitted any documents to department
Client has closed office on 2016 hences all physical notice return to department
Hences they are calling for this matter in this month

I want to know from your opinion on this case
what's is time limit for department can pass Order in services tax Matters for F Y 13-14 and 14-15 or already time barr 5 year Completed.

Thanks