Quite recently people have been seeing the nominal interest rate on their credit card statements which is usually lower than their annual percentage rate due to the need for certain fee disclosures.
The nominal interest rate is your rate on your credit card. The annual interest rate, if higher, usually is because of a fee that has been charged for such things such as foreign transaction fees, membership fees, statement fees, and other fees. The fees for a balance transfer usually can cause your APR to be very high, so it is important that you calculate this when your consider this type of transfer.
Nominal interest rate is your periodic interest rate times (X) the periods per year. So if you have 18% interest rate your interest rate would be 1.5% per month or 18% / 12 months. A fee included in your calculation of your interest rate would make your APR higher due to the need to show the fee in the calculaton.
The Truth in Lending Act is the act that mandates that lenders disclose interest rates in a clear and concise way. Regulation Z is the standard set by the Federal Reserve Board that all lenders must use to calculate the APR.