A credit card is a loan you take out one purchase at a time

When you swipe or tap a credit card, you are borrowing money from the card issuer — the bank or financial company that issued the card. The merchant gets paid immediately. You get a bill later, usually 20 to 25 days after your purchase, asking you to pay back what you borrowed. If you pay the full balance by the due date, you owe nothing extra. If you pay only part of it, the card issuer charges you interest on the amount you did not pay back.

That interest is the card issuer's profit. The percentage they charge is called the APR, or annual percentage rate. A card with a 20% APR means that if you carry a $1,000 balance for a full year without paying it down, you will owe $200 in interest on top of the original $1,000. Most cards charge interest monthly, not yearly, so the math works out to roughly one-twelfth of the APR each month.

The card issuer makes money three ways: interest from people who carry balances, interchange fees (a small percentage the merchant pays every time you use the card), and annual fees (which some cards charge just for holding them). You only pay the interest and annual fees — the interchange fee is between the merchant and the card issuer.

Key Takeaways

  • A credit card is a short-term loan: you borrow money to pay a merchant, then pay the card issuer back within a grace period, usually 20 to 25 days.
  • If you pay your full balance by the due date, you pay no interest; if you pay only part of it, interest accrues on the remaining balance at the card's APR.
  • Your credit limit is the maximum you can borrow at once, and exceeding it usually triggers an over-limit fee and a higher interest rate.
  • Every purchase and payment is reported to the credit bureaus and affects your credit score, which lenders use to decide whether to lend to you and at what rate.

How the payment cycle works

Each month, the card issuer sends you a statement. This statement lists every purchase you made during the billing cycle — usually a 28 to 31 day period — and shows you three important dates: the statement date (when the cycle ended), the due date (when payment is due), and the grace period (the number of days between the statement date and the due date).

Most cards offer a grace period of at least 21 days. During this time, you can pay your balance in full with no interest charged. The grace period applies only to new purchases, not to balances you carried from the previous month. If you had a balance last month and did not pay it off completely, interest is already accruing on that old balance, and the grace period does not stop it.

You have three payment options: pay the full balance (best for your finances), pay the minimum payment (usually 1 to 3 percent of your balance, set by the card issuer), or pay any amount in between. Paying only the minimum keeps your account in good standing, but the rest of your balance starts accruing interest immediately after the grace period ends.

What happens when you carry a balance

Carrying a balance means you did not pay off your full statement balance by the due date. Starting the day after the grace period ends, interest begins accruing on the unpaid amount. The card issuer calculates this daily: they take your APR, divide it by 365, multiply by your current balance, and add that to what you owe. This happens every single day until you pay the balance to zero.

This is why carrying a balance is expensive. If you have a $2,000 balance on a card with a 18% APR and you pay only the minimum each month, it will take you roughly two years to pay off the card, and you will pay about $400 in interest. If you could pay $200 a month instead, you would pay it off in 10 months and pay only about $80 in interest. The faster you pay, the less interest you owe.

Some cards offer a promotional APR — a lower interest rate for a set period, often 0% for 6 to 21 months. This is useful if you need to carry a balance temporarily, but the regular APR kicks in after the promotional period ends, usually at a higher rate than you would get on a regular card.

Credit limits and what happens when you exceed them

Your credit limit is the maximum amount you can borrow on the card at any one time. The card issuer sets this based on your credit score, income, and payment history. A higher credit score usually means a higher limit. You can request a higher limit, and the issuer will review your account and either approve or deny the request.

If you try to make a purchase that would push you over your limit, the card issuer will usually decline the transaction. Some cards allow you to exceed your limit if you opt in to over-limit protection, but this comes with a fee — typically $25 to $35 per occurrence — and a higher interest rate. Exceeding your limit also damages your credit score, so it is best to avoid it.

Your credit limit does not reset each month. It is the maximum you can owe at any point. As you pay down your balance, your available credit increases. If you have a $5,000 limit and a $2,000 balance, you have $3,000 in available credit to borrow.

How credit cards affect your credit score

Every purchase, payment, and missed payment on your credit card is reported to the three major credit bureaus: Equifax, Experian, and TransUnion. This information is used to calculate your credit score, a three-digit number that lenders use to decide whether to lend to you and at what interest rate.

Several factors affect your score. Payment history — whether you pay on time — accounts for about 35% of your score. Credit utilization — the percentage of your available credit that you are using — accounts for about 30%. If you have a $5,000 limit and a $2,500 balance, your utilization is 50%. Most lenders prefer to see utilization below 30%. Length of credit history, credit mix (having different types of credit, like cards and loans), and new credit inquiries make up the rest.

Missing a payment by 30 days or more will significantly damage your score and will stay on your credit report for seven years. Even one missed payment can lower your score by 100 points or more. Paying on time, every time, is the single most important thing you can do to build and maintain good credit.

Fees you might encounter

Beyond interest, credit cards can charge several types of fees. An annual fee is a flat charge just for holding the card, usually $25 to $500 depending on the card's benefits. A late fee is charged if you miss your due date, typically $25 to $40 for the first late payment and up to $40 for subsequent ones. A returned payment fee is charged if a payment you made bounces due to insufficient funds in your bank account.

A cash advance fee is charged if you withdraw cash from an ATM using your credit card instead of a debit card. This fee is usually 3 to 5% of the amount withdrawn, with a minimum of $5 to $10. Cash advances also start accruing interest immediately — there is no grace period — and the interest rate is often higher than your regular APR.

A foreign transaction fee is charged if you use your card outside the United States, usually 1 to 3% of the purchase amount. Some cards waive this fee as a benefit. An over-limit fee is charged if you exceed your credit limit, typically $25 to $35.

How merchants and card networks fit in

When you use a credit card, several parties are involved. You are the cardholder. The merchant is the store or business where you are making the purchase. The card network — Visa, Mastercard, American Express, or Discover — is the company that processes the transaction and sets the rules both you and the merchant must follow. The card issuer is the bank or financial company that issued your card and lends you the money.

Here is what happens in the seconds after you swipe: the merchant's payment processor sends your transaction to the card network. The card network checks that your card is valid and that you have not exceeded your limit, then sends the request to your card issuer. The issuer approves or declines the transaction and sends the response back through the network to the merchant. If approved, the merchant is paid by the card network within one to three business days, and the purchase appears on your statement.

The merchant pays a fee for this service — the interchange fee mentioned earlier — which is a percentage of the transaction amount, usually 1 to 3%. This is why some merchants offer discounts for paying with cash or debit: they save money by avoiding the card network fee.

Frequently Asked Questions

What is the difference between a credit card and a debit card?

A debit card draws money directly from your bank account, so you can only spend what you have. A credit card borrows money from the card issuer, which you pay back later. Debit cards do not build credit history; credit cards do. Credit cards offer fraud protection and rewards; debit cards usually do not.

Why does my credit card statement show a different balance than what I owe?

Your statement balance is what you owed on the statement date. Your current balance is what you owe right now, which may include new purchases made after the statement date. You only owe interest on the statement balance if you do not pay it in full by the due date. New purchases made after the statement date have their own grace period.

Can I use a credit card to pay off another credit card?

Most card issuers do not allow you to pay one credit card with another credit card. You can use a balance transfer, which moves your balance from one card to another (usually with a 3 to 5% fee), but this is different from a regular payment. Balance transfers are useful if you are moving to a card with a lower APR or a promotional 0% rate.

What happens if I never use my credit card?

If you never use your card, the issuer may close the account after a period of inactivity, usually 6 to 12 months. A closed account can lower your credit score because it reduces your total available credit. To keep the account open, use it occasionally — even a small purchase every few months is enough — and pay the balance in full.

Is it better to pay my balance weekly or wait until the due date?

Paying weekly does not reduce interest if you pay the full balance by the due date, because the grace period covers the entire billing cycle. However, paying early can lower your credit utilization if the card issuer reports your balance to the credit bureaus mid-cycle, which may slightly boost your credit score. Paying early also reduces the risk of accidentally missing the due date.