Can My NDA Stop Me from Joining a Client's Sister Company After My Notice Period?

If I have completed 90 days of the notice period completely, can an employer deny me a relieving letter and F&F, considering I have joined a sister company of the client company? I have a clause in the NDA that I shouldn't join the client company for one year. Can it prevent me from joining the sister company of the client company?

Legally, nothing should prevent your movement. However, it depends on the policies of the relieving firm and the joining firm. If your relieving company is aware of your plans to join a client's associate, they might create problems. Watch out.