1
general::
Late or behind, especially in payment of money. For example, He's been in arrears on his rent so often that he may be evicted. [First half of 1600s]
American Heritage Idioms
2
general::
Phrase(s): *in arrears
[of debts; of an account] overdue. (*Typically: be ~; get ~.) • Jane’s student-loan payments are in arrears. • The accounts of the bankrupt company were in arrears.
McGrawhill's American Idioms And Phrasal Verbs