I called the FL Dept of Business & Professional Regulation & was told it was 18%. I asked if it had to say 18% in the contract or could I charge the 18 AFTER the account was past due, the customer service rep was not sure. He referred me to FL Statute 687:
"INTEREST AND USURY; LENDING PRACTICES"
687.03 "Unlawful rates of interest" defined; proviso.--
(1) Except as provided herein, it shall be usury and unlawful for any person, or for any agent, officer, or other representative of any person, to reserve, charge, or take for any loan, advance of money, line of credit, forbearance to enforce the collection of any sum of money, or other obligation a rate of interest greater than the equivalent of 18 percent per annum simple interest, either directly or indirectly, by way of commission for advances, discounts, or exchange, or by any contract, contrivance, or device whatever whereby the debtor is required or obligated to pay a sum of money greater than the actual principal sum received, together with interest at the rate of the equivalent of 18 percent per annum simple interest.