Child support cannot be modified retroactively. This is the so-called Bradley Amendment, one of the provisions of 42 U.S.C. Section 666(a)(9) that Congress required each state to adopt in 1986 or forfeit significant federal funding. The Maryland legislature enacted the provision as follows:
Family Law Section 12-104. Modification of child support award.
(a) Prerequisites. – The court may modify a child support award subsequent to the filing of a motion for modification and upon a showing of a material change of circumstance.
(b) Retroactivity of modification. – The court may not retroactively modify a child support award prior to the date of filing of a motion for modification.
The law was intended to keep parents from running up large child support arrearages and then having a sympathetic judge forgive or erase them.
Fathers don’t like it because it means that if they are laid off, are sent to Iraq, become disabled, spend time in jail or just have a cash flow emergency, they must move to modify child support. If they don’t, the meter keeps running on child support and it cannot be set back.
Mothers don’t like it because they can’t get child support increases back to when there income goes down or the father’s income goes up, if they are slow to file their petition with the court.