I had checked into this and meant to respond previously but forgot! Based on something I read on the
Florida state site, I think you had best get some official guidance on this questios. The state may very well want to full tax (which has now been capped at $2,450.)
"Mortgages, Liens, and Other Evidences of Indebtedness
Documentary stamp tax is due on a mortgage, lien, or other evidence of indebtedness filed or recorded in Florida. The tax rate is $.35 per $100 (or portion thereof) and is based on the amount of the indebtedness or obligation secured, even if the indebtedness is contingent. When a mortgage, lien, or other evidence of indebtedness is given to secure a previously unsecured indebtedness or obligation upon which the maximum tax of $2,450 was paid, tax is due on the full amount of the indebtedness or obligation secured, minus the $2,450 already paid."
Apparently the old documentary stamps were quite onerous, making trips offshore wellworth while in the case of sizeable loans. One example said that the stamps on a $25,000,000 loan would have cost $85,000! It was cheaper to hire a boat and captain and head out to sea.