tuyen said:
CIC doesn't know about your credit cards, nor do they want to know. They don't check anything to do with your personal finances, other than what they ask for from the sponsor to show that he/she isn't on welfare.
CIC does want to know, as it shows proof of shared financial accounts. The don't care about the balance or debts is probably what you mean. For common-law couples it's even specifically stated on the declaration form: "Have joint bank, trust, credit union or charge card accounts... yes or no?"
Anytime you can show joint finances, utilities, lease/mortgage, insurance etc... it adds proof to a relationship.
Of course timing is irrelevant. CIC would have no way of knowing when you got the joint accounts and you don't need to tell them, so it makes no difference if it was just before mailing the app or not.