Maryland Code, Real Property § 11B-112.1

The declaration or bylaws of a homeowners association may provide for a late charge of $15 or one-tenth of the total amount of any delinquent assessment or installment, whichever is greater, provided the charge may not be imposed more than once for the same delinquent payment and may be imposed only if the delinquency has continued for at least 15 calendar days.