The Professional Ethics Committee of The Florida Bar has stated that there is no ethical prohibition against a lawyer charging a lawful rate of interest on liquidated fees or costs. A lawyer who wishes to charge interest on past due accounts, however, must do so either: (1) by written agreement with the client; or (2) in the absence of a written agreement, by giving the client reasonable notice of the intent to begin charging interest. The Committee viewed 60 days as constituting reasonable notice. See Opinions 86-2, 71-26.
If you have questions about the aforementioned opinions you may contact the Ethics Hotline at 800.235.8619.