The letters "PM" on a license plate in Florida stand for "permanent". This is a new type of registration sticker that has been introduced for rental car companies in Florida. The yellow decal will have "PM" printed on it in place of the month and year expiration, and the paper registration will have "Permanent Decal Issued" printed on it. The permanent sticker is reserved for rental services, and it is unlikely that anyone else will be able to get the same treatment unless they own a similar business.