100 %Exempt Income

As per Section 23 of CGST Act .
Person is not liable to grant registration:
a) any person engaged exclusively in the business of supplying goods or
services or both that are not liable to tax or wholly exempt from tax under this Act or
under the Integrated Goods and Services Tax Act;

So Registration is not required if you are dealing 100% in exempted Supply

Refer Section 23 of the CGST Act 2017...
"PERSONS NOT LIABLE FOR REGISTRATION".

Can you give any circular or notification please

Dear Stark

when it's given in Act , then why you need Notification or circular.

Sec 23 will give the relaxation not to take registration. however if you have taken GST Number then Audit become compulsory u/s 35(5) of CGST act.