If you serve a break notice on behalf of a client, it is good practice to state that you are acting as the client’s agent.

If you do not, then there is the possibility of the notice being challenged (in which case you would have to show that you were authorised to give notice, and that in the circumstances the other side could act upon the notice safe in the knowledge that it was binding). To avoid arguments, always say that you serve as an agent of the client.