A credit card is a loan you use one transaction at a time
When you use 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 monthly, and you decide how much of that bill to pay back. If you pay the full balance, you owe nothing extra. If you pay only part of it, the issuer charges you interest on the amount you leave unpaid, and that interest accrues daily until you pay it off.
The card issuer makes money two ways: from interest you pay on unpaid balances, and from fees the merchant pays every time you swipe. You are the customer of the issuer, not the merchant. The merchant is also a customer of the issuer — they pay to accept your card. This is why some small businesses offer discounts for cash: they avoid the merchant fee.
Understanding how a card works means understanding four separate things: how the transaction happens, how interest is calculated, what fees you might pay, and what happens to your account when you do not pay.
Key Takeaways
- A credit card transaction borrows money from the issuer on your behalf; the merchant is paid immediately, and you receive a bill later.
- Interest accrues daily on any unpaid balance at a rate called the APR, which varies by card and by your creditworthiness.
- You can avoid interest entirely by paying your full statement balance by the due date each month.
- Late payments trigger late fees and can raise your interest rate, and unpaid debt is reported to credit bureaus and affects your credit score.
- Closing a card does not erase the debt on it, and it can lower your credit score by reducing the total credit available to you.
How a transaction moves from merchant to your bill
When you swipe, insert, or tap your card at a merchant, the card reader sends your card number and the transaction amount to the payment processor — a company that handles the technical side of moving money. The processor checks with your issuer to confirm you have not exceeded your credit limit (the maximum you are allowed to borrow on this card) and that your account is not frozen or closed.
If the issuer approves, the merchant's bank receives the money within one to three business days. You do not pay anything yet. Instead, the transaction appears on your account as pending, meaning it has been approved but not yet finalized. Pending transactions count toward your credit limit even though the money has not left your account.
After a few days, the transaction moves from pending to posted. Posted transactions are final. They appear on your monthly statement along with every other transaction from that billing cycle. Your statement shows the date the cycle ended, the date your payment is due (usually 21 to 25 days later), and the minimum payment you must make to avoid a late fee.
How interest is calculated on unpaid balances
Every credit card has an Annual Percentage Rate, or APR. This is the yearly interest rate the issuer charges on money you borrow. A card with a 20% APR charges 20% per year on any balance you do not pay off. The actual daily rate is the APR divided by 365. On a 20% APR card, that is roughly 0.055% per day.
Interest accrues daily on your average daily balance — the average of what you owed each day during the billing cycle. If you charged $1,000 on day one and paid $500 on day 15, your average daily balance for that cycle is not $750. It is calculated by adding up what you owed each day and dividing by the number of days in the cycle. This is why paying early in the cycle saves you more interest than paying late in the cycle: you reduce the number of days you carry the higher balance.
Interest is added to your balance on the first day of the next billing cycle. If your statement shows a balance of $1,000 and an interest charge of $16.67, that $16.67 is now part of what you owe. If you make no payment, next month's interest will be calculated on $1,016.67, not $1,000. This is called compounding. Over time, unpaid interest grows faster than the original debt.
You can avoid all interest by paying your full statement balance by the due date. The statement balance is the total of all transactions posted during that billing cycle, minus any payments you made during the cycle. Paying only the minimum does not avoid interest — it only avoids a late fee.
Fees that appear on your account
A late fee is charged if your payment arrives after the due date. The amount varies by issuer and by state law, but typically ranges from $25 to $40 for the first late payment in a year, and higher for repeat late payments. A payment is considered late if it is received after 11:59 p.m. on the due date, even if you mailed it on time. Online payments usually post the same day if submitted before the cutoff time, which is often 5 p.m. Eastern time.
A returned payment fee is charged if a check or ACH transfer bounces because there is not enough money in your bank account. This fee is separate from any overdraft fee your bank charges.
An over-limit fee is charged if you exceed your credit limit. Many issuers no longer charge this fee, but some do. You can usually prevent it by opting out of over-limit protection, which means transactions will be declined if they would push you over your limit.
A foreign transaction fee is charged when you use the card outside the United States, usually 1% to 3% of the transaction amount. Some cards waive this fee as a benefit.
An annual fee is charged once per year just for having the card, regardless of whether you use it. Premium cards often charge $95 to $500 or more per year. Cards with no annual fee are common and are often a better choice if you do not use the card frequently.
What happens when you do not pay
If your payment is 30 days late, the issuer reports the late payment to the three major credit bureaus: Equifax, Experian, and TransUnion. This report stays on your credit report for seven years. A 30-day late payment damages your credit score significantly — typically a drop of 100 points or more, depending on your score before the late payment.
At 30 days late, your interest rate usually increases to the penalty APR, which is the highest rate allowed by law for your card type. This rate applies to new transactions and sometimes to your existing balance, depending on your card's terms. The penalty APR can be 29.99% or higher.
If your payment is 60 days late, the issuer may freeze your account, meaning you cannot make new charges. If your payment is 90 days late, the issuer may charge off the account, meaning they remove it from their active accounts and sell the debt to a collection agency. A charge-off stays on your credit report for seven years and makes it very difficult to borrow money in the future.
If the debt is sold to a collection agency, the agency can contact you by phone, email, or mail to demand payment. They can also sue you in court to recover the debt. If they win, they can garnish your wages or place a lien on your property, depending on your state's laws. The collection account also appears on your credit report and damages your score.
How closing a card affects your account and credit
Closing a credit card does not erase any debt on it. If you have an unpaid balance when you close the card, you still owe that balance and still pay interest on it until it is paid off. The issuer may continue to report the account to credit bureaus, and late payments continue to be reported even after the account is closed.
Closing a card can lower your credit score because it reduces your available credit — the total amount you are allowed to borrow across all your cards. Credit scoring models reward you for using only a small portion of your available credit. If you close a card with a $5,000 limit and you have $15,000 in debt on other cards, your credit utilization jumps from 75% to 100%, which lowers your score.
If you want to close a card, pay off the balance first, then contact the issuer and request closure. Ask the issuer to confirm the account is closed and to note in your file that you requested the closure. Keep the confirmation in writing. The account will remain on your credit report for ten years after closure, but it will show as closed, which is better than showing as closed by the issuer.
How payments are applied to your balance
When you make a payment, the issuer applies it in a specific order set by federal law. Payments are applied first to any fees owed (late fees, over-limit fees, and so on), then to interest, then to the principal balance — the original amount you borrowed. This order means that if you are behind on payments, most of your payment goes toward fees and interest, not toward reducing what you actually owe.
If you have multiple balances on one card — for example, a regular purchase balance and a balance transfer at a lower rate — the issuer applies your payment to the balance with the highest interest rate first. This is required by law and works in your favor.
Payments usually post to your account within one to three business days of submission. If you submit a payment online or by phone before the cutoff time on the due date, it is considered on time even if it does not post until the next day. If you mail a check, it must be received by the due date to be on time; the date you mailed it does not matter.
How credit cards report to credit bureaus
Your issuer reports your account activity to the credit bureaus once per month, usually around the same date each month. The report includes your account balance, your payment history, your credit limit, and whether your account is current, 30 days late, 60 days late, or in charge-off status.
The report does not include every transaction. It includes only the balance at the end of the billing cycle and whether you made your minimum payment on time. If you pay your full balance every month, the bureaus see a $0 balance and a on-time payment, which is excellent for your credit score. If you carry a balance, the bureaus see that balance and report it as debt you owe.
Your payment history makes up 35% of your credit score. A single late payment can lower your score by 100 points or more. On-time payments, even small ones, build your score over time. After 24 months of on-time payments, a late payment's impact on your score begins to fade, though it remains on your report for seven years.
Frequently Asked Questions
Do I have to pay interest if I pay my full balance by the due date?
No. If you pay the entire statement balance by the due date, you pay zero interest. This is true even if you carried a balance the previous month. The interest-free period applies to new purchases made during the current billing cycle, as long as you pay the full balance on time.
What is the difference between my statement balance and my current balance?
Your statement balance is what you owed at the end of your last billing cycle. Your current balance includes transactions posted since the statement closed, plus any interest or fees added since then. You should pay your statement balance to avoid interest. Paying only your current balance may leave you short if new transactions have posted.
Can the issuer raise my interest rate without warning?
Yes, but only under certain conditions. If you make a late payment, the issuer can apply a penalty APR to your account. If your card's terms allow it, the issuer can also raise your regular APR if you make a late payment. The issuer must notify you in writing before the rate increase takes effect, usually 45 days in advance. You can close the account to prevent the new rate from applying to future transactions, though it still applies to your existing balance.
What happens if I ignore a collection agency?
Ignoring a collection agency does not make the debt go away. The agency can sue you in court, and if they win, they can garnish your wages, freeze your bank account, or place a lien on your property, depending on your state's laws. The collection account also remains on your credit report for seven years, making it difficult to borrow money. Responding to the agency or negotiating a settlement is usually better than ignoring them.
Does paying off a card early hurt my credit score?
No. Paying off a card early does not hurt your score. Paying off your balance reduces your credit utilization, which improves your score. The only downside is that you stop building a payment history on that card, but the benefit of lower utilization outweighs that. Paying on time matters far more than paying early.