⏰ Credit Card Late Payment Interest Calculator

What is credit card default interest, and what does this tool calculate?

Default interest (gecikme faizi) is the interest charged on the unpaid part of the minimum payment shown on your statement. The rest of the statement debt carries contractual interest (akdi faiz). Both are topped up by two Turkish charges equal to a share of the interest itself, BSMV and KKDF, so what you actually pay is higher than the interest line.

The tool models one statement period for a personal card: a Turkish-lira purchase statement, one payment made by the due date, and 1–30 days after it. You enter the statement debt, the minimum payment, the amount paid, the number of days and the two rates; it shows default interest, contractual interest, a daily net interest reference, total net interest, BSMV, KKDF, the interest and taxes for the period and the estimated remaining due. The whole result is listed under the form without opening anything.

It is an estimate, not your bank's final figure. Balances carried over from earlier cycles, new purchases, several payments, compound interest, fees, restructuring, corporate cards and foreign-currency cards are not included.

Late interest on cash withdrawals and cash advances is outside this tool and is not calculated here, because it carries a different rate from card purchases. The linked Credit Card Cash Advance Installment Calculator is not a replacement: it estimates the repayment schedule of an installment cash advance (installment, interest, KKDF and BSMV breakdown) and does not calculate late interest on an overdue cash withdrawal. To spread purchases over installments see the Credit Card Installment Calculator, and to restructure card debt see the Credit Card Balance Restructuring Calculator.

What is the difference between default interest and contractual interest?

Contractual interest (akdi faiz) is the card's ordinary interest; default interest (gecikme faizi) is a usually higher rate that applies only to the unpaid part of the minimum payment. Article 20(3) of the Banking Regulator's card regulation, as quoted in the BDDK's 2007 press statement, says exactly this: if you pay less than the minimum, default interest applies to the unpaid part of the minimum and contractual interest to the part of the remaining balance above the minimum. The same provision rules out compound interest on card debts, default included.

• Pay the whole minimum or more, and no default interest arises; only contractual interest and its taxes run on the remaining balance.
• Pay less than the minimum, and default interest runs on the part of the minimum you did not pay while contractual interest runs on the rest.
• Default interest is never charged on the whole balance: its base is only the missing slice of the minimum.
• Interest is not charged on interest, and the tool does not add interest to principal to compound it.

How are the interest and taxes calculated?

Each interest is the monthly rate divided by 30 and multiplied by the number of days. The steps are:

1. Remaining principal = statement debt − amount paid.
2. Default-interest principal = minimum payment − amount paid (0 if negative).
3. Contractual-interest principal = remaining principal − default-interest principal.
4. Default interest = default principal × monthly default rate × days ÷ 30; contractual interest = contractual principal × monthly contractual rate × days ÷ 30.
5. Net interest = the sum of the two, kept at full precision; BSMV and KKDF are each 15% of that net interest and each is rounded to the kuruş on its own.
6. Interest and taxes for the period = net interest + BSMV + KKDF; estimated remaining due = remaining principal + that amount.

The daily net interest is a reference only and is not used in the calculation, so the total is never a rounded daily figure times the days. For that reason the two displayed interest lines can differ from net interest by one kuruş. Rounding the two taxes separately matters too: on 241.50 TL of net interest each tax is 36.225 TL, which rounds half-up to 36.23 TL, for a total of 313.96 TL; adding 30% in one rounded step would show 313.95 TL.

Which rates should you use? The central bank's maximum rates

By default the tool uses the row dated 1 October 2026 of the Central Bank of the Republic of Türkiye (TCMB / CBRT) table of maximum credit card interest rates. The tier is chosen by the original statement debt on the statement, not by the remaining balance:

• Statement debt below 30,000 TL: monthly contractual 3.25%, default 3.55%.
• Statement debt from 30,000 TL to 180,000 TL (both included): monthly contractual 3.75%, default 4.05%.
• Statement debt above 180,000 TL: monthly contractual 4.25%, default 4.55%.

The edges are a hard step: with a statement debt of 29,999.99 TL and a 6,000 TL minimum, 30 days cost 1,290.90 TL in interest and taxes; at 30,000.00 TL under the same conditions it is 1,485.90 TL. The difference comes from the tier changing, not from one kuruş of debt.

The last tier of the CBRT table is also stated to apply to corporate credit cards regardless of statement debt. This tool covers personal cards; for a corporate card you would have to enter your own contract rate, and the result would still be an estimate.

How do you enter the minimum payment? The banking regulator's 1 October 2026 decision

The most reliable input is the minimum payment printed on your statement, and the form asks for that figure directly. If you do not know it, tick "I don't know the minimum payment": you can then estimate it from your card limit or use a percentage that is your own assumption, typed or taken from the 25%, 27%, 30%, 35% and 40% quick picks. The quick picks are conveniences only, not official or default rates.

The BDDK (Banking Regulation and Supervision Agency) Board Decision No. 11581 of 1 October 2026 sets the minimum under Article 22(7) of the card regulation: 20% of the statement debt if the card limit is 100,000 TL or below, 40% if it is above 100,000 TL. 100,000 TL itself belongs to the lower category, so a limit of exactly 100,000 TL gets 20% and one kuruş more gets 40%. The previous decision (No. 10970, 26 September 2024) set the threshold at 50,000 TL.

When the limit estimate is chosen, the minimum is the relevant percentage of the statement debt rounded half-up to the kuruş; the 10 TL floor or whole-lira round-up seen on some online calculators is not applied. When a percentage is chosen, the figure you type or pick is not treated as an official rate and the result is labeled a user assumption. The card limit is required for the limit estimate; the statement debt is never used in its place.

How should you read the results?

• Estimated interest and taxes for the period: net interest, BSMV and KKDF together; the extra cost that builds up over the days you chose.
• Estimated remaining due: the unpaid principal plus that extra cost, the debt this calculation expects by the next statement.
• Principal charged default interest and principal charged contractual interest: the amounts each interest runs on; together they equal the remaining principal.
• Default interest and contractual interest: the two components shown separately; default interest is 0 once you pay at least the minimum.
• Daily net interest: a comparison reference only, roughly the total divided by the days.
• Rates used: each rate's source, either the CBRT maximum or your own entry, is written on its row.

Examples: how the amount paid changes the result

In the examples below the statement debt is 10,000 TL, the minimum payment on the statement is 4,000 TL, the delay is 15 days unless stated, and the rates are the CBRT ceilings dated 1 October 2026 (contractual 3.25%, default 3.55%).

• If nothing is paid, 30 days add 438.10 TL in interest and taxes and the estimated remaining due is 10,438.10 TL: 142.00 TL default interest (on 4,000 TL), 195.00 TL contractual interest (on 6,000 TL), 50.55 TL BSMV and 50.55 TL KKDF.
• Pay 2,000 TL and be 15 days late: default interest is 35.50 TL (on 2,000 TL), contractual interest 97.50 TL (on 6,000 TL), BSMV and KKDF 19.95 TL each; interest and taxes 172.90 TL, estimated remaining due 8,172.90 TL.
• Pay exactly the 4,000 TL minimum: default interest over 15 days is 0 and only 97.50 TL of contractual interest runs on 6,000 TL. BSMV and KKDF each round from 14.625 TL to 14.63 TL; the total is 126.76 TL and the estimated remaining due 6,126.76 TL.
• Pay 6,000 TL: the minimum is exceeded, so there is no default interest; the remaining 4,000 TL carries 65.00 TL of contractual interest and 9.75 TL of each tax over 15 days, 84.50 TL in all, leaving 4,084.50 TL due.
• Pay the whole 10,000 TL statement debt: interest, taxes and remaining due are all 0, and the tool does not treat this as an error.

With your own rates: a 10,000 TL statement debt, 4,000 TL minimum, 1,000 TL paid, 30 days, contractual 2.50% and default 3.00% give 90.00 TL default interest on 3,000 TL and 150.00 TL contractual interest on 6,000 TL. Net interest is 240.00 TL, BSMV and KKDF 36.00 TL each, interest and taxes 312.00 TL and the estimated remaining due 9,312.00 TL.

A limit-based example: a 75,000 TL statement debt with a 90,000 TL card limit (below 100,000 TL, so 20%) gives a reference minimum of 15,000 TL. With 5,000 TL paid and 20 days (tier 3.75 / 4.05), default interest is 270.00 TL on 10,000 TL, contractual interest 1,500.00 TL on 60,000 TL, interest and taxes total 2,301.00 TL and the estimated remaining due is 72,301.00 TL.

Common mistakes and misunderstandings

• Thinking default interest runs on the whole balance: it runs only on the missing part of the minimum; the rest carries contractual interest.
• Thinking interest stops once the minimum is paid: default interest stops, but contractual interest and taxes keep running on the remaining balance.
• Picking the rate tier from the remaining balance: the table follows the original statement debt, so paying the balance below 30,000 TL does not change the tier.
• Treating the CBRT rate as your bank's rate: the table gives ceilings and your bank may charge less.
• Replacing the figure on your statement with the regulator's limit-based 20% / 40% rule: the text does not say which statements it applies to, so enter the statement amount.
• Leaving out BSMV and KKDF, or adding 30% to total interest in one rounded step: the tool calculates and rounds the two separately.
• Using this tool for cash-advance arrears: cash withdrawals carry a different rate and this tool models only the purchase statement. The linked installment cash-advance calculator does not calculate late interest either, only a repayment schedule, so the two are not interchangeable.

Taxes: BSMV and KKDF

Personal credit card interest carries 15% KKDF (Resource Utilization Support Fund) and 15% BSMV (Banking and Insurance Transactions Tax). The revenue administration's ruling on card interest states that KKDF must be calculated on interest-type amounts for consumer credit cards; the 15% BSMV rate was set by Presidential Decision No. 7345. The tool shows only these two items on interest; BSMV on card fees and commissions is not included.

Scope and limitations

• The tool models a personal card's lira purchase statement and one period. Debt carried over from earlier periods, new purchases, several payments, fees, restructuring, corporate or foreign-currency cards and cash advances are outside it.
• The payment is assumed to be made by the due date and the delay is a whole number from 1 to 30 days. 0 or 31 days is rejected.
• The statement debt must be above zero, the minimum cannot exceed the statement debt, and the payment must be between 0 and the statement debt with at most two decimals. An invalid value shows no result.
• Changing a value or pressing Reset removes the previous result; press Calculate for a new one. Reset returns the fields to an empty starting state.
• If your bank's interest start date, statement cut-off day, rounding or contract rate differ, the actual amount changes. The binding figure is on your bank statement; the tool is informational and is not a bank offer or legal or financial advice.