Credit card companies can adjust your APR, but only in specific situations and often with advance notice, especially under U.S. rules shaped by the Credit CARD Act and later guidance.

The big picture: when they can raise APR

In general, a card issuer can change your APR in four main ways:

  1. After the first 12 months of the account
    • For the first year, they usually cannot raise the APR on new purchases unless an exception applies (like a variable index change or serious delinquency).
 * After the account has been open at least 12 months, they can increase the APR for future purchases if they:
   * Give you at least 45 days’ written notice, and
   * Apply the higher rate only to new transactions made at least 14 days after that notice.
  1. When a promotional or temporary APR ends
    • If you have a temporary intro rate (for example 0% APR on purchases or balance transfers for 6–12 months), the issuer can raise the APR to the standard “go‑to” rate once that promo period expires.
 * They do not need an extra 45‑day notice for this, because the promotional end date and the post‑promo APR should have been disclosed in your original offer and card agreement.
  1. If you have a variable APR and the index changes
    • Many cards use a variable APR tied to an index like the U.S. Prime Rate, expressed as “Prime + a margin.”
 * When the index rate goes up or down, your APR can automatically move with it, and the issuer typically does not have to give 45 days’ advance notice of that change.

 * Example: If your APR is “Prime + 17%” and Prime rises from 7% to 7.5%, your APR can rise from 24% to 24.5% without a special rate‑increase notice.
  1. Penalty APR after serious delinquency
    • If your minimum payment is more than 60 days late, the issuer may apply a much higher “penalty APR” to your existing balance and new transactions.
 * They must send you a 45‑day advance notice describing the new penalty APR and when it will apply.

 * Under later rules, they must also review that penalty APR at least every six months to see if it can be reduced.

When they usually cannot raise APR on existing balances

Issuers are generally restricted from raising the APR on your existing balance, with some exceptions.

They typically cannot raise the rate on what you already owe except when:

  • A temporary promotional rate on that balance ends.
  • Your minimum payment has been more than 60 days late and a penalty APR is applied.
  • You agreed to a workout or hardship plan that changes your rate, and then you either complete it or fail to follow its terms.
  • Certain protections (like military SCRA rate caps) expire.

For all other “standard” APR hikes, the higher rate generally applies only to future purchases, not to the balance you already carried before the change took effect.

How notice and timing work

Most non‑penalty and non‑variable‑index APR increases follow this pattern:

  • 45‑day advance notice
    • You must get written notice at least 45 days before the new APR takes effect.
    • The notice must explain what is changing and when.
  • 14‑day buffer for new transactions
    • Any purchases made more than 14 days after that notice are treated as “new transactions” and can be charged the higher APR.
  • Ongoing review of increased APR
    • If your rate was increased (for example, after a general re‑pricing or penalty), the issuer generally has to review your account at least every six months to assess whether the APR can be reduced.

Helpful way to think about it

You can think of APR changes as falling into three buckets :

  • Built‑in changes
    • Variable APR tied to an index, promotional APR ending.
    • Mostly automatic and disclosed up front; no extra 45‑day notice requirement.
  • Behavior‑based changes
    • Serious late payments (60+ days), defaulting on a hardship plan, or similar risk signals.
    • Can trigger penalty APR that may apply to existing balances, with required notice and later reviews.
  • Business decision changes
    • Issuer decides to re‑price cards after the first year (for risk, market, or policy reasons).
    • Requires 45‑day notice and applies to future purchases only.

Summary (TL;DR):
A credit card company can adjust your APR when a promo ends, when a variable index like Prime moves, after your account is at least 12 months old (with 45 days’ notice for future purchases), or if you’re over 60 days late and they impose a penalty APR on existing and new balances.

Information gathered from public forums or data available on the internet and portrayed here.