Originally Posted by wm47

I have done this a number of times and National is generally pretty flexible, but, as pointed out by others in this thread, the rate may change. Also, some car classes may convert from unlimited miles to a per mile charge, even on a corporate rate. This happened to me once when returning to IAD -- when I arrived they initially tried to charge me over a thousand dollars (I had driven maybe 400 miles).. But to their credit, they removed the charge right away when I noted that the customer service phone agent did not disclose that the miles allowance changed from unlimited to a per-mile charge when I called to change the return location.