National who/where told you this? I use my corporate contract all the time for personal rentals. Our rate includes insurance. I did have a minor accident on a personal rental using the rate. National said the insurance didn't apply (makes sense), and instead my insurance would need to be involved. AMEX stepped in on the claim. National didn't tell me that I could not use my rate, just that all benefits don't apply. Never had a problem adding Missus Duxfan. But I also don't give some counter agent more info than they can process. When you ask a question like "this is a personal rental using my corporate rate, can I add a driver?" It gives the agent an opening to add a fee that usually results in a commission for them.