No, it is not necessary under law to have a written agreement with your commissioned agent or with any person, for that matter. As per the provisions of the Contract Act, a contract or agreement may be written or unwritten. In fact, the contract may be implied also, which means a contract may be inferred from the circumstances or conduct of the parties even if there was no formal contract (whether written or unwritten).
So, the law does not make it mandatory to have a written agreement or contract. It is up to you if you want to have a formal written contract, mentioning all necessary details to avoid any future complications. Choice is yours. If you have good understanding with the person concerned, you may deal with him without a formal written agreement. At the same time, if you want, you can have a written agreement with him. Just keep in mind that sometimes it may be advisable to have a written agreement with all necessary terms and conditions if you want to avoid any future confusion. But, as I mentioned above, it is the choice of the parties concerned.
Dr. Ashok Dhamija is a New Delhi based Supreme Court Advocate and author of law books. Read more about him by clicking here. List of his Forum Replies. List of his other articles. List of his Quora Answers. List of his YouTube Videos.