I certainly applaud your patience in that case :-) . On a related note, this particular topic seems to be a good one to create a wiki post. However it is somewhat "across all cards" so not sure where the appropriate place would be. DoC also has an article on adding AU's and its impact on various things but it also fails to capture this particular data point (i.e which company reports what date). In general, based on DP's from Chase, C1 and AmEx, the rule of thumb seems to be that if the AU's credit card number is the same as the primary user's number, the AU's date will be the same as the primary user's opening date but if the AU's get issued a different credit card number (which is the case with AmEx), then the date on CR will be the date when the AU's card was opened.