No more than 1 Citi business application in 90 days (95 to be safe).
Wiki also says, some had to totally cancel their business CC before applying in order to get approved. Does that mean, you apply for the CC, get bonus within 3 months, close the account and you can apply again after 95 days?
Wouldn't they ask, you had just closed the same account? Is the identical business card churnable after 95 days? or there has to be small change from card to card like Visa, MC or Elite, Platinum, world etc