Child custody agreements can be modified over time in the event that circumstances change within the lives of the parents or the child which causes the agreement to no longer be in the best interest of the child. Examples which could include domestic violence, a custodial parent has been sentenced to jail, the custodial parent has an addiction to drugs or alcohol. Child custody arrangements can be modified at any point necessary up to the age of majority as set out by the state of residence, which is typically set at the age of 18. If you desire to change the current custody arrangement, you must file an order with the court to change the legal agreement. You can hire an attorney to complete this process on your behalf, or you can download the change forms on the website of your family court system.