Originally Posted by
ChateauMargaux
Does this rule count only personal credit cards from the past 12m or business cards as well?
Assuming you're applying for a personal card, they're going to count only cards that appear on your credit report. Business cards from most banks don't appear on personal credit reports, but business cards from some banks (like Discover still, and previously Capital One) can appear on personal credit reports.
Just check your own credit report for free, for example at Credit Karma, and in case you closed any cards already that you opened within the past 12m, check the closed cards section too. Credit Karma will show the open date of each card, but it won't sort by that date AFAIK, so you have to look through the list and find the cards that are within the past 12m and count them yourself. By checking your own credit report for all cards (open and closed) opened within 12m (BofA) or 24m (Chase), you can figure out exactly what count the bank will see.