It is critical that the rental be before the entry of final judgment. If so you can move to amend the judgment to reduce the judgment by the amount to be collected under the new lease. Even if the rental occurred after the judgment and you did not appeal it, I would still make the motion to amend based on mistake because they were able to rent it and if the judgment stands it would unjustly enrich the landlord. The motion would be made under rule 1.540(b) of the rules of civil procedure. Here is the text of the rule.
On motion and upon such terms as are just, the court may relieve a party or a party‘s legal representative from a final judgment, decree, order, or proceeding for the following reasons: (1) mistake, inadvertence, surprise, or excusable neglect; (2) newly discovered evidence which by due diligence could not have been discovered in time to move for a new trial or rehearing; (3) fraud (whether heretofore denominated intrinsic or extrinsic), misrepresentation, or other misconduct of an adverse party; (4) that the judgment or decree is void; or (5) that the judgment or decree has been satisfied, released, or discharged, or a prior judgment or decree upon which it is based has been reversed or otherwise vacated, or it is no longer equitable that the judgment or decree should have prospective application. The motion shall be filed within a reasonable time, and for reasons (1), (2), and (3) not more than 1 year after the judgment, decree, order, or proceeding was entered or taken. A motion under this subdivision does not affect the finality of a judgment or decree or suspend its operation. This rule does not limit the power
May 20, 2013 Florida Rules of Civil Procedure 114of a court to entertain an independent action to relieve a party from a judgment, decree, order, or proceeding or to set aside a judgment or decree for fraud upon the court
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