Originally Posted by sdsearch

To be specific, Chase evaluates 5/24 by going through your credit report and counting all cards (open and closed) showing there with an "opened on" date in the past 24 months.

The reason business cards from most banks don't count towards 5/24 is because business cards from most banks don't show up on personal (EQ/EX/TU) credit reports, as long as the account is kept "in good standing". There are exception banks though: Discover and Capital One both report their business cards to EQ/EX/TU, and so business cards from at least those two banks do count against 5/24.

The simplest way to evaluate your 5/24 is to sign up for a free account at Check Your Credit Report & FICO ® Score Experian. Experian's site (without having to use any tricks) lets you sort your accounts (open and closed in separate lists) by the open date (the rightmost column) and so it's easy to quickly spot the cards that were opened in the last 24 months that way. (Experian will urge you to sign up for a paid account, but decline and keep your free account. The paid account is not worth it for most people.)