Thanks, Dan. I wasn't aware of this option, and doubt it was available when we initially got our transponder (ours is the old O-pass) because we discussed our situation with a supervisor at the time who only suggested we register one of our cars from Denmark. I'll have to try to log into the account online and see if it can be done.

In this case, I doubt it would have helped because the only tolls that the transponder failed to register were the first day, on our drive from the airport just after collecting the car to our flat. So we weren't in a position to have gotten the rental registered yet. It's the first time in multiple trips per year over the past six years that we've had this problem.

Susan