Go and read the policy and small print - by using a credit card the first time you agree that unless you call them they can take from that card for any future changes or renewals - so when your renewal comes through if you don't want it you have to notify them otherwise they take the amount automatically ( I know this from experience four years ago when I first went with Admiral multicar) Also when you stop to read NCB terms on the multi-car you will find that she can only accrue NCB on the car she is the main driver for. Note difference between 'main driver' and actual 'policy holder' - I also found this out to my expense when my partner pranged the zed and it was me that lost my NCB as I was policy holder. Read things through and make no assumptions!