If you want to use a joint credit card for family expenses, due to the cash-back feature, I guess you could do that. Both debit and credit cards generate billing detail (transparency), but I suppose you could do this. But under no circumstances should you pay HER credit card(s). If she's putting all of the her day-to-day needs (haircuts, gas, OTC drugs, etc.) and the kids' needs (and reasonable wants) on the joint credit card, and you are both making contributions into the joint account based on the proportions of each of your incomes . . . then there's no reason for you to pay HER cc's, for her to spend on secret affair phones, drinks with OM or her own enabling BFFs, etc.
