Specific forms required to modify child custody differ from state to state, but many states provide printable forms online, which are available at FindLaw.com. In some cases, parents may write their own custody modification agreements without going back to court, according to Rocket Lawyer.
Parents who write their own custody modification agreement should ask a notary public to witness their signatures to preclude future disputes. Lacking any mutual agreement, parents must file legal petitions to submit a proposed custody modification to the court, according to Rocket Lawyer. Some states require parents to work with a mediator to work out custody modification details, as in California and Kentucky.