Miss. Code § 75-17-27
A late payment charge, not exceeding Five Dollars ($5.00) or four percent (4%) of the amount of any delinquency, whichever is greater, if contracted for in writing, shall not be considered a finance charge, but no such charge shall be made unless such delinquency is more than fifteen (15) days past due; provided, however, that such late payment charge may be collected only one (1) time on a specific installment and no late payment charge may be collected on a partial payment resulting from the deduction of a late payment charge from a regular scheduled payment. On loans of One Hundred Thousand Dollars ($100,000.00) or less having a stated maturity of five (5) years or less, such late payment charge shall in no event exceed Fifty Dollars ($50.00).
Miss. Code § 75-17-27