Lately I stopped adding the rental car to my Sunpass account. It has not been a problem
Normally it won't be a problem. You put the plate info on the account to serve as a 'backup'. To review what I've explained b4 .... here's a quik overview of how the electronic systems work (in FL anyway)
car drives past/under a 'reader'
1. system looks for a transponder (in the car) ... if found charge the account; if no, continue
2. electronically 'read' the tag, search individual account database (SUNPASS / E-PASS) for the tag .... if found charge the account; if no, continue
(if you don't PUT the tag info in the system you shut this backup off .... sometimes the readers just MISS the transponder .... dunno why)
3. check the 'fleet registration' file for the tag {this is where the major rental companies and things like truck companies and taxi companies have their accounts) ... if found charge the account; if no, continue (how the rental company passes this charge to you is where the different rental company policies come in to play as well as crazy service charges. The COMPANY paid the regular toll rate .... what they charge you however . . . )
4. If all this fails the toll is handled as an 'exception' and what happens differs by WHERE in the state (FL) the toll was. In ELECTRIC ONLY areas like MIAMI a bill is sent once a month to the registered owner (plus a small service charge) this is classic 'toll by plate'. In the Orlando area where CASH is an option, you have 'run a toll' and may very well receive a ticket in the mail. In experience I've seen few reports of this happening for ONE infraction ... but each additional one makes the odds go UP.
There are a lot of details left out but this is the basics. I can tell you from experience that correctly entered info can avoid problems. I've driven toll roads with my SUNPASS not even in the car ... but the tolls where charged to my account .... no harm, no foul (or should I say that dd drove for months not realizing the SUNPASS we provided her was sitting on her desk and not in the car!! "Hey, what's your SUNPASS doing sitting here?" )
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So be sure to take the license plate out of your account as soon as you return the car.
In the SUNPASS APP for the PORTABLE transponder, when you add a vehicle and ID it as a rental you can enter an EXPIRE day/time ..... to prevent 'forgetting' like this.