Credit cards, explained

Part of Financial 101 — free, plain-language reference guides. Not personalised advice. Download the one-page Order of Operations checklist.

The one rule

Pay the full statement balance every month, by the due date, forever. If you do that, a credit card costs you nothing, builds your credit history, and hands you whatever rewards it offers as pure upside. If you do not, it becomes one of the most expensive forms of borrowing available to ordinary people, and the rewards are a distraction from that fact. Every other paragraph on this page is a footnote to this one.

How the interest actually works

People misunderstand this in a way that costs them money, so it is worth being precise.

Each month the card closes a statement. Between the statement date and the due date — the grace period, which by law must be at least 21 days — you owe no interest on purchases, provided you paid last month’s statement in full. Pay in full again and the cycle continues; you have borrowed money for free for up to seven weeks.

Carry a balance — pay less than the full statement amount — and two things happen at once. Interest is charged on the unpaid amount, calculated daily, at an annual rate that is typically far above any other consumer loan. And you lose the grace period: new purchases start accruing interest from the day you make them, not from the due date. Which means the month after you carry even a small balance is more expensive than it looks, and getting back to zero requires paying that statement in full plus any trailing interest.

Paying the minimum is the trap inside the trap. Minimums are set low enough that a balance can take many years to clear, with most of each payment going to interest. The card statement shows you this arithmetic in a box, by law. Read the box once.

Rewards: tool or bait

Issuers offer points and cash back because rewards cards are profitable — from interchange fees merchants pay, and from the minority of cardholders who carry balances. For someone who pays in full, a rewards card is a small rebate on spending they were doing anyway. Fine. Take it.

The failure mode is spending to earn. A two percent reward on a purchase you would not otherwise have made is a 98 percent loss. Sign-up bonuses with spending thresholds, category multipliers, and annual-fee cards with lounge access all push the same way: toward more transactions, and toward the feeling that the card is on your side. A simple no-fee card with flat cash back, paid in full, captures most of the benefit with none of the incentives to overthink it.

Annual fees

Worth paying only if you would genuinely use the benefits without changing your behaviour to justify them — and if the arithmetic works after the fee. Most people are better served by no fee. If you already have an annual-fee card and the benefits have stopped mattering, ask the issuer to downgrade it to a no-fee version rather than closing it; that preserves the account’s age for your credit score.

A few mechanics worth knowing

Autopay the statement balance. Not the minimum. Not a fixed amount. The full statement. Then check the statement monthly for errors, because autopay does not.

Utilisation is reported at the statement date. A high balance on the closing date can dent your score even if you pay it off the next day. Not a reason to pay early every month, but useful to know before a mortgage application.

Cash advances carry a fee and start charging interest immediately, with no grace period. Avoid them.

Balance transfers with a promotional rate can be a rational way to clear existing debt faster, provided you stop adding to it and clear the balance before the promotional period ends. Read the transfer fee and the go-to rate.

Disputes and fraud protection are a real advantage over debit cards: a fraudulent charge on a credit card is the bank’s money while it is investigated, not yours.

If you already have card debt

It moves up the order of operations to step three, ahead of everything except the starter emergency fund and the employer match. Paying off a balance at a high double-digit rate is a guaranteed, tax-free return that no investment can promise. Stop using the card, pay as much as you can above the minimum, and consider whether a balance transfer or a fixed-rate personal loan lowers the cost while you do it.

Checklist

One or two no-fee cards · Autopay set to full statement balance · Statements reviewed monthly · No cash advances · Rewards treated as a rebate, never a goal · Any existing balance on a written payoff plan.

Related: Credit scores · Banking basics · Emergency fund