I provided signs to a customer and they dont want to pay.
What types of signs did you provide? Are they permanently attached to the real property? If not, then you might not have a lien right.
Assuming you do, under 713.08, Florida Statutes, you are entitled to include finance charges in your lien. If you have concerns over making sure the lien amount is correct, you should consult with an attorney to ensure that you get the amounts right. Otherwise your lien could be declared fraudulent.