Back rent is a rent owing from an earlier date. It is a rent due or in arrears but not paid. Rent is the consideration paid periodically for use or occupancy of property.
Back rent is a debt within the meaning of the Fair Debt Collection Practices Act, 15 USCS § 1692a., and thus a demand for back rent may be a communication from a debt collector. [Backuswalcott v. Common Ground Community HDFC, Inc., 104 F. Supp. 2d 363 (S.D.N.Y. 2000)]
In English law, back rent is the full extended value of land let by lease, payable by tenant for life or years.