Often a credit card issuer offers a low or zero percent APR on purchases for a limited time, known as an introductory period. This promotional period may last anywhere from three months to 21 months and will remain in effect as long as all payments are made on time, the credit limit is not exceeded, and all conditions of the card are met. If a customer goes into default, the introductory period will no longer apply. After the period ends, the regular ongoing APR will apply to any balance carried.