Arrears are money that is overdue to be paid; typically refers to child support or alimony that has not been paid on time.
Merriam-Webster Online Thesaurus
arrears (noun plural)something (as money) which is owed
SYNONYMS:
arrearage, arrears, indebtedness, liability ( liabilities), obligation, scoreRELATED WORDS:
bond, debit, delinquency; bankruptcy, default, embarrassment, insolvencyNEAR ANTONYMS:
quietus, quittance, repayment; asset