(a) A landlord of a residential building may not charge a late fee if the rent is paid after the due date, unless the tenant and landlord have agreed in writing that a late fee may be imposed. The agreement must specify when the late fee will be imposed. In no case may the late fee exceed eight percent of the overdue rent payment. Any late fee charged or collected is not considered to be either interest or liquidated damages. For purposes of this paragraph, the "due date" does not include a date, earlier than the date contained in the written or oral lease by which, if the rent is paid, the tenant earns a discount.
(b) Notwithstanding paragraph (a), if a federal statute, regulation, or handbook permitting late fees for a tenancy subsidized under a federal program conflicts with paragraph (a), then the landlord may publish and implement a late payment fee schedule that complies with the federal statute, regulation, or handbook.