The rule in plain English
Florida gives a landlord two mutually exclusive paths when a tenancy ends. Returning the deposit in full: 15 days. Keeping any part of it: written notice of the claim within 30 days, in the wording s. 83.49(3)(a) prescribes, by certified mail (or e-mail only under a signed s. 83.505 addendum). A landlord who misses the 30-day notice window forfeits the right to deduct from the deposit and must return it — a damages lawsuit remains possible, but the deposit itself goes back.
After a proper notice, the tenant has 15 days from receipt to object in writing. If no objection comes, the landlord deducts the claim and returns any balance within 30 days after the date of the notice.