Modification forms are filed with the Probate and Family Court where the judgment/order was originally issued. See Where do I file? for court contact information.
Where do I file if I or the other parent has moved away?
If both you and the defendant live in this state, but in different counties, you must file in the county where your case was originally heard. For example, if you were divorced in Norfolk County, but you now live in Suffolk County and the defendant in Plymouth County, you must file in Norfolk Probate and Family Court.
If the other parent lives in a different state, the Massachusetts Child Custody Jurisdiction Act applies. This law determines which state’s court has the authority (jurisdiction) to change a custody agreement. This link is to the first section of the law and contains the definition of a child’s “home state.” If Massachusetts qualifies as the home state, the case may be heard in this state. Other conditions also may apply. Read the statute carefully. You may want to get legal advice in this situation. See Find a Lawyer in Massachusetts for help in finding an attorney.