Credit card APR changes come from a short list of causes: the benchmark index your variable rate is tied to moved, a promotional period ended, you triggered a penalty rate, or your issuer sent you a formal notice of a change. Each one has different rules behind it, and in several cases you have rights that can blunt or reverse the increase.
Variable Rates Move With the Prime Rate
Nearly every credit card issued today carries a variable APR. Your card agreement sets a “margin,” and your rate equals the U.S. Prime Rate plus that margin. The Prime Rate tracks about three percentage points above the federal funds rate set by the Federal Reserve, so when the Fed moves, the Prime Rate moves, and your APR moves with it.
You will not get a letter or a phone call when this happens. Because the change comes from a publicly available index outside the issuer’s control, federal regulations exempt variable-rate adjustments from the advance notice rules that apply to other rate increases.1eCFR. 12 CFR 1026.55 – Limitations on Increasing Annual Percentage Rates, Fees, and Charges The new APR simply shows up on your next statement.
Fixed-rate cards still exist but are uncommon. A fixed rate does not drift on its own with the Prime Rate, but the issuer can still change it after sending a written notice at least 45 days in advance. “Fixed” means the rate does not move automatically, not that it is locked forever.
Your Promotional Rate Expired
Introductory 0% APR offers are one of the most common reasons people see a sudden jump on a statement. These promotions run for a set period — commonly 12, 15, 18, or 21 months — and federal rules require they last at least six months.1eCFR. 12 CFR 1026.55 – Limitations on Increasing Annual Percentage Rates, Fees, and Charges When the clock runs out, the rate reverts to the standard APR disclosed when you opened the account. That standard rate depends on the creditworthiness you had at application. Someone with excellent credit might land at 18%, while someone with a thinner file could see 27% or higher.
Any balance still on the card when the promotional period ends starts accruing interest at the full standard rate from that point forward. The issuer does not need to send a separate notice, because the terms were disclosed upfront. Even a small remaining balance converts from interest-free to fully interest-bearing overnight.
Deferred Interest Is Not the Same as 0% APR
This distinction trips up more consumers than almost anything else in credit card lending. A true 0% introductory APR means no interest accrues during the promotional period. If a balance remains when the promotion ends, interest starts accumulating only on that remaining amount going forward.
Deferred interest works differently. The language typically reads “no interest if paid in full within 12 months” rather than “0% intro APR for 12 months.” Interest is actually accruing the entire time, silently, in the background. Pay the full balance before the deadline and that accrued interest vanishes. Leave even a dollar unpaid when the promotional period expires and the issuer charges you all the interest that accumulated since the original purchase date.2Consumer Financial Protection Bureau. How to Understand Special Promotional Financing Offers on Credit Cards Deferred interest offers show up most often on store credit cards and medical financing. The difference between “0% APR” and “no interest if paid in full” can cost hundreds of dollars on a modest balance.
A Late Payment Triggered a Penalty APR
Missing a payment by more than 60 days can trigger a penalty APR, often the highest rate your issuer charges. Penalty rates commonly land around 29.99%, though the exact number varies by card. Federal law bars issuers from imposing this increase before the 60-day delinquency threshold, so a payment that is a few days or even a month late cannot push you to the penalty rate.3Office of the Law Revision Counsel. 15 USC 1666i-1 – Limits on Interest Rate, Fee, and Finance Charge Increases Applicable to Outstanding Balances
The penalty rate is not necessarily permanent. The same statute requires the issuer to end the increase within six months if you make every minimum payment on time during that period. The issuer must also include a clear written explanation of why the rate went up and a statement that the increase will end if you stay current for six months.3Office of the Law Revision Counsel. 15 USC 1666i-1 – Limits on Interest Rate, Fee, and Finance Charge Increases Applicable to Outstanding Balances Here is the sting: the penalty APR can apply to your existing balance, not just new charges. A $5,000 balance you were carrying at 21% could jump to 29.99% across the board.
Your Issuer Sent a 45-Day Notice
When an issuer wants to raise your rate for reasons other than a variable-rate index change, expiration of a promotional period, or the 60-day late payment trigger, federal law requires 45 days’ written notice before the increase takes effect.4eCFR. 12 CFR Part 1026 Subpart B – Open-End Credit The notice must spell out what is changing, when it starts, and your right to reject the change.
That right to reject is more powerful than most cardholders realize. If you notify the issuer before the effective date that you do not accept the new terms, the issuer cannot apply the increase to your account. They also cannot charge you a fee or treat your account as in default just because you said no.4eCFR. 12 CFR Part 1026 Subpart B – Open-End Credit The tradeoff is that the issuer will likely close your account to new purchases. But you keep the right to pay off your existing balance at the old rate and on terms no less favorable than your original repayment schedule.
Watch for those notices in the mail. They look like junk, and plenty of people throw them away. The 45-day window is your only chance to opt out before the new rate locks in.
Which APR Actually Changed?
A single credit card does not have just one interest rate. Your statement may show separate APRs for purchases, balance transfers, and cash advances, plus a possible penalty rate on top of those. Each applies independently to its own slice of your balance, and each can move for different reasons.
Cash advances deserve special attention. The cash advance APR is typically higher than the purchase APR, and there is no grace period. Interest starts accumulating the day you withdraw cash. With a regular purchase, you get at least 21 days to pay your statement balance in full before any interest kicks in. Cash advances skip that window entirely. If your statement interest jumped and you recently used your card at an ATM or for a cash-equivalent transaction, that is likely why.
Ask Your Issuer for a Lower Rate
You can call your card issuer and ask for a rate reduction, and it works more often than you would expect. This is a negotiation, not a formal process. Your leverage depends on how you have managed the account: a long history of on-time payments, low utilization, and an improved credit score since you opened the card all strengthen your case.
Before you call, look up current offers from competing issuers. If a rival card offers a meaningfully lower rate for someone with your credit profile, mention it. Issuers would rather trim your margin by a point or two than lose the account. If the first representative says no, ask for a supervisor; supervisors typically have more authority to adjust terms. Be direct and respectful. The person on the other end can see your entire payment history on their screen.
If you do not qualify today because of recent late payments or high balances, focus on those fundamentals for six months and try again. Rate reductions are not one-shot opportunities.
Rate Caps for Active-Duty Military
Two separate federal protections limit credit card interest rates for active-duty servicemembers and their dependents. They apply in different situations and can save thousands of dollars.
The Military Lending Act caps the interest rate on new consumer credit at 36%, and the calculation includes not only the stated APR but also fees, credit insurance premiums, and add-on products sold with the credit.5Office of the Law Revision Counsel. 10 USC 987 – Terms of Consumer Credit Extended to Members and Dependents: Limitations This “all-in” rate means an issuer cannot work around the cap by loading up on fees while keeping the stated APR under 36%. The MLA also prohibits prepayment penalties.6Consumer Financial Protection Bureau. Military Lending Act (MLA)
The Servicemembers Civil Relief Act provides an even lower cap for debts that predate military service. If you took on credit card debt before entering active duty, you can request that the interest rate be reduced to 6% for the duration of your service. The excess interest above 6% is forgiven entirely, not deferred.7Office of the Law Revision Counsel. 50 USC 3937 – Maximum Rate of Interest on Debts Incurred Before Military Service To claim the benefit, send your creditor a written request along with a copy of your military orders. You have up to 180 days after your service ends to submit the request.8U.S. Department of Justice. Your Rights as a Servicemember: 6% Interest Rate Cap for Servicemembers on Pre-Service Debts For joint debts, both the servicemember and spouse must be named on the account to receive the rate reduction.