The minimum bid, also known as the minimum CPC, is the least that one can pay to have an ad appear for a particular keyword in a particular account. It is very important to know, however, that one’s minimum bid is entirely unrelated to how many other advertisers are using the same keyword. Instead, since August of 2005, the minimum bid has been quality based. To put it simply, the higher the Quality Score of a keyword, the lower one’s minimum bid will be for that keyword.