beattyfamily is correct. There is a distinction between the DC contract code and a DC coupon (such as the one for 1 free day with a weekend rental which is currently available). The contract code starts with a 5. The coupon code starts with a 1. You can use one (and only one) contract code and one (and only one) coupon code. The National web site will flag an incorrect entry of either number and also flags expired coupons. For the DC contract code, you need to have your DC membership number (most easily provided by carrying the card along). For a coupon code, you need the coupon (which can be printed at the DC site if you did not receive it in the mail or have already used it, like I did last month). I used both together and have a ressie for mid-July for a week-long rental again using both contract and coupon codes. I just hand my printed copy of the coupon and my DC card to the attendant at the kiosk when I leave the EA.
Ralph