Originally Posted by 0re0

TxTag also uses a pay by mail system, too, based on your plate registration. I have used this throughout the Austin and Houston areas with no problem with my rental car company, but I use the same pick up location and asked the guy what would be best. He said they just charge the tolls (plus a minimal fee from the tollway for billing, just a couple bucks per billing period) directly to my rental after drop off. I was a little skeptical, since years of living on the east coast had taught me that I would be slammed with additional fees from the rental company for going through express lanes, but I guess because this pay by mail thing is built into the Texas system, the company doesn't penalize you.