When you see credit card offers touting no interest for a long time, sometimes as much as 18 months, it may not be clear how the companies make money. The credit card industry is packed with thousands of different options. Credit card companies know that interest rates are important to consumers, especially those who often carry a balance. The credit card company has you as a customer, but you can use their card interest-free for the duration of the introductory period, which could be well over a year. The true test for credit card issuers is whether you will keep using the card once the no-interest period ends. But as your introductory period nears its end, start paying down your balance.