What Is Balance Transfer APR and How Does It Work?

A balance transfer APR is the interest rate your credit card issuer charges on debt you move onto the card from another lender. It applies only to the transferred amount and sits separately from the rates on new purchases and cash advances. Most balance transfer cards advertise a promotional 0% rate lasting anywhere from 6 to 21 months. Once that window closes, whatever balance remains starts accruing interest at a variable go-to rate, usually somewhere between 17% and 28% depending on your credit and the current prime rate.

Federal rules require the issuer to disclose that balance transfer rate, and the method used to calculate interest on it, before you open the account.¹ You will find it in the standardized disclosure box on every credit card application, listed alongside the purchase APR and the cash advance APR. If the rate is variable, the disclosure must say so and identify the index used to set it.²

How the Promotional 0% Rate Works

The introductory rate is the whole reason people move a balance. Federal law requires any promotional rate to last at least six months.³ The most competitive cards run the 0% offer for 15 to 21 months. During that stretch, every dollar you pay reduces principal because no interest is accruing on the transferred balance.

When the promotional period ends, any leftover balance begins accruing interest at the regular variable APR the issuer disclosed up front. The issuer cannot charge more than that disclosed rate on balances that built up during the promotion.⁴ As of early 2026, the prime rate sits at 6.75%, and issuers layer a margin on top based on your credit profile.⁵ Good credit generally lands you in the 17% to 22% range after the promotion. Thinner credit files can push the post-promotional APR to 25% or higher.

True 0% APR Versus Deferred Interest

This is the distinction that costs people the most money. A true 0% APR promotion means no interest accrues during the promotional period. If you still owe $2,000 when the promo expires, interest starts running on that $2,000 going forward. Nothing is charged retroactively for the months the balance sat at 0%.⁶

A deferred interest offer looks similar but works differently. If you fail to pay the balance in full by the deadline, the issuer charges interest retroactively on the entire original balance, dating back to the transaction. The CFPB says to watch for the word “if” in the offer: “no interest if paid in full within 12 months” points to deferred interest, while “0% intro APR for 12 months” points to a true zero-percent promotion.⁶ Most balance transfer credit cards use true 0% APR promotions. Deferred interest shows up more often on store cards and point-of-sale financing.

The Transfer Fee

The 0% rate is not the full price of the transfer. Nearly every card charges an upfront fee of 3% to 5% of the amount moved, usually with a minimum around $5. Transfer $10,000 at a 3% fee and you add $300 to the balance the moment the transaction posts. At 5%, that becomes $500. A few cards waive the fee, but they generally offer shorter promotional windows or higher go-to rates in exchange.

The fee changes the break-even math. If you are escaping a card at 22% interest, the interest saved during the promotional period needs to exceed the 3% to 5% you pay to move the debt. On balances you plan to carry for at least several months, the arithmetic usually favors the transfer. On small balances or short payoff timelines, the fee can absorb most of the savings.

How Interest Is Calculated Once It Kicks In

Once interest starts accruing, either after the promotion ends or on a transfer without a promotional rate, it is calculated daily. The issuer divides the APR by 365 or 360 days (the card agreement specifies which) to produce a daily periodic rate.⁷ That daily rate gets applied to your average daily balance for the billing cycle.

What that looks like in practice: a $5,000 balance at 20% APR produces a daily rate of about 0.055%, or roughly $2.74 in interest per day. Across a 30-day billing cycle, that runs to about $82. Because the calculation runs on the average daily balance, a payment sent early in the cycle reduces interest more than the same payment sent on the due date.

How Payments Are Applied to Different Balances

Cards often carry balances at more than one rate at the same time. Say you have a $6,000 transfer at 0% and $1,500 in new purchases at 22%. Federal regulations require issuers to apply any payment above the minimum to the highest-APR balance first, then work down.⁸ If your minimum is $100 and you pay $500, the extra $400 goes toward the 22% purchase balance before it touches the 0% transfer.

The minimum payment itself is a different matter. Issuers generally have discretion over how to allocate the minimum, and most send it to the lowest-rate balance first. That is why financial advisors tell you not to make new purchases on a balance transfer card. Every dollar you spend creates a high-rate balance that keeps growing while the minimum payment gets absorbed by the 0% portion.

What Happens if You Pay Late

Missing a payment can cost you far more than a late fee. If a payment arrives more than 60 days past due, the issuer can revoke the promotional rate and apply a penalty APR to the entire outstanding balance.⁹ Penalty rates commonly exceed 29%.

There is a safety valve, but it is narrow. If the issuer raises your rate because of delinquency and you then make the next six consecutive minimum payments on time, the issuer must bring the rate back down.⁴ Six months at a penalty APR on a large balance is still expensive. Automatic minimum payments are cheap insurance against losing a promotional rate.

Grace Periods and New Purchases

Most credit cards give you a grace period on purchases: pay the full statement balance by the due date and you owe no interest on those purchases. Balance transfers generally do not get a grace period. During a 0% promotion the promotion itself is your interest-free window, but the grace period mechanism is a separate feature.¹⁰

The bigger issue is what carrying a transfer does to purchases. If you have a $5,000 transferred balance on the card, even at 0%, you are carrying a balance. New purchases may start accruing interest from the day of the transaction unless you pay the entire balance, transfer included, in full by the due date.¹¹ The clean approach is to use the balance transfer card only for the transfer and put day-to-day spending on a different card.

What Determines the Rate You Get

Issuers advertise balance transfer APRs as ranges, such as “0% intro APR for 18 months, then 17.49% to 27.49% variable.” Where you fall in the range depends mostly on your credit score. The longest 0% promotions, in the 18 to 21 month range, generally go to applicants with a FICO score of 670 or higher. Scores in the 740-plus range tend to receive the lowest post-promotional variable rates.

The variable rate itself has two parts: the prime rate, currently 6.75%, plus a margin the issuer sets based on your credit profile.⁵ A margin of 11% produces a variable APR of 17.75%. When the Federal Reserve changes its benchmark rate, the prime rate moves with it and your variable APR adjusts on the same schedule. You get no advance notice of these adjustments because the change is built into the card agreement as an automatic, index-based update.¹

1
eCFR. 12 CFR 1026.6 – Account-Opening Disclosures
2
Consumer Financial Protection Bureau. 1026.60 Credit and Charge Card Applications and Solicitations
3
Office of the Law Revision Counsel. 15 USC 1666i-2 – Additional Limits on Interest Rate Increases
4
eCFR. 12 CFR 1026.55 – Limitations on Increasing Annual Percentage Rates, Fees, and Charges
5
Federal Reserve. H.15 – Selected Interest Rates (Daily)
6
Consumer Financial Protection Bureau. How to Understand Special Promotional Financing Offers on Credit Cards
7
Consumer Financial Protection Bureau. What Is a Daily Periodic Rate on a Credit Card
8
eCFR. 12 CFR 1026.53 – Allocation of Payments
9
Office of the Law Revision Counsel. 15 USC 1666i-1 – Limits on Interest Rate, Fee, and Finance Charge Increases Applicable to Outstanding Balances
10
Consumer Financial Protection Bureau. What Is a Grace Period for a Credit Card
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Consumer Financial Protection Bureau. Do I Pay Interest on New Purchases After I Get a Zero or Low Rate Balance Transfer