On his podcast, Clark Howard answers real reader questions on money, credit, debt, retirement, travel, and more, along with co-host Christa DiBiase.

Clark's answer: It all depends on how that particular credit card company calculates payments.

Do they put payments toward the regular bill, and let's say you're paying that regular balance in full — are they still charging you interest on it because you have an outstanding "Pay Over Time" balance?

In other words, some credit card issuers segregate the Pay Over Time program. You pay interest on that portion, but your standard purchases remain interest-free as long as you pay the regular bill in full. Other card issuers treat it differently: as long as you have an open Pay Over Time balance, you lose your grace period and pay interest on every single transaction on the bill.

That distinction is really the key criteria here.