• Many Americans have multiple credit cards.three credit cards image by Aleksandr Ugorenkov from Fotolia.com
  
  Credit cards are one of the more convenient ways to make purchases, including large and emergency purchases that might not be possible with cash. However, credit card users are subject to several different types of rules and regulations whenever they use a credit card. While each card is different, there are some basic rules every cardholder should be aware of.
  
  

Credit Limits

• Most credit cards have a credit limit, which is a dollar amount based on the cardholder's income and credit history. A credit card's total balance, including fees, purchases and any prior balance, may not exceed the credit limit. This is what leads some merchants to reject cards in cases where the user has surpassed the credit limit.
  
  Credit limits are designed to prevent the user from making excessive purchases that they are unlikely to be able to pay off. However, credit card companies also thrive on the interest users pay on such purchases, so a cardholder's limit is likely to increase over time as long as timely payments continue.
  
  

Due Dates

• Credit card users must pay monthly bills whenever the card has a balance. Users can choose to pay a minimum amount (usually set as a particular dollar amount based on a percentage of the balance), a higher amount or the full balance. Whatever the payoff amount, each monthly payment is due by a specific date. However, there is no limit on when an individual purchase, or the entire card balance, must be paid off.
  
  

Interest

• Credit card users are also required to pay interest on purchases. Interest accrues when a cardholder pays less than the full balance of the card for a given month. Card issuers calculate monthly interest as a percentage of the remaining balance and add it to the following month's bill. Each credit card may set its own interest rate, and variable rates are common. Cardholders may also fall under rules that place a higher interest rate on cash advances, which are also borrowed against the card's balance.
  
  

Other Fees

• Credit card issuers often charge customers additional fees, only some of which apply to purchases. Annual fees and monthly maintenance fees are common and usually appear on cards that offer higher credit limits or other perks. Cardholders may be subject to overage fees if they make purchases above their credit limit, as well as late fees on overdue payments and balance transfer fees for moving debt between credit cards.
  
  

Rewards

• Many credit cards also offer a rewards program, offering airline miles, cash rebates or discounted goods and services. Card issuers specify rules that govern how everyday purchases earn reward value, usually based on the dollar amount charged to the card. These rewards points may also feature an expiration date, or a minimum limit on when they are available for redemption.