Who owns a joint account during the lifetime of the joint parties?

A joint account belongs to the parties in proportion to the net contributions of each party to the balance unless there is clear and convincing evidence of a differing intent. If you and your parent have a joint account and all of the funds in the account were deposited solely by your parent, the money in the account belongs to your parent. When you sign a check, the funds must be used for the benefit of your parent, unless they agree to allow you to use their funds for your own needs. If you write a check to yourself, it could be a gift or a loan from your parent if approved by your parent.