Greetings Nalathu,
Why don't you contact your certification body directly? I suggest this, cause though the guidlines are same, the documentation or the process needed by the certification body may vary, comparing to other countries or even other CB.
If by client you mean the receiver, then you only need him to maintain the traceability documents. If you mean the client that trades his products through you, then he should be treated as a supplier, no matter the deal (GMP, available analyses of the products if needed, traceability documents, compliance with legislation, maybe some certification though not really needed, storage/transportation conditions etc).
Regards!