Late-Payment Interest in Turkey: 2026 Rate and Calculation

“I missed it; there will be one penalty” usually lands as one line on the desk. The file often opens two: the principal and late-payment interest. Interest grows until the payment day. The rate is not fixed forever; a Presidential Decree can change it. On a long debt, each stretch uses the rate then in force.

This guide is the 2026 rate, the maths, and how it differs from delay interest. Due days sit in the monthly tax calendar. Try your own figures on the late-interest calculator. The same line is read beside the assessment slip in our Kızılay office in Ankara.

What attracts late-payment interest?

It attaches to an assessed public receivable whose payment period has expired. Taxes, duties, fees and many other claims chased under Law 6183 sit in that set. Social-security premium arrears also show a late-payment line; the period breakdown is on the collection screen.

Interest does not start before the due date. Once the return is filed, the tax is assessed and the payment day has passed, the clock runs from the end of that due date. If no return was filed, other sanctions (irregularity, tax loss) may apply; interest still runs on unpaid principal and on eligible penalties.

A statutory minimum applies: late-payment interest cannot fall below the legal floor. A few days of delay can still open a line; “it is only a few days” does not hold in the file.

What is the 2026 rate?

The current rate is 3.7% per month from 13 November 2025 (Presidential Decree 10556, Official Gazette 33076). The previous stretch was 4.5% per month from 21 May 2024 (Decree 8484). When the rate changes, the new rate applies only to time after the change; earlier days keep the old rate.

The source is the Revenue Administration’s late-payment rate table. Check the decree in force on the payment day before you lock a figure. The same rate feeds delay interest under TPL 112 and voluntary-disclosure interest under TPL 371.

How is it calculated?

For full months: principal × monthly rate × number of months. For a partial month: (monthly rate ÷ 30) × days. Default practice is not compound interest; each month is read on the principal. If the rate changes mid-way, split the period.

Example 1 — two full months: 50,000 TL of VAT due 28 March, paid 28 May, all inside the 3.7% period. Interest = 50,000 × 0.037 × 2 = 3,700 TL. Total due 53,700 TL.

Example 2 — months plus days: 10,000 TL, three full months and ten days at 3.7%. Three months: 10,000 × 0.037 × 3 = 1,110 TL. Ten days: 10,000 × (0.037 ÷ 30) × 10 ≈ 123 TL. Interest about 1,233 TL; total about 11,233 TL.

After three months, interest is about 11% of the principal. Waiting a quarter often costs more than a month of accounting fees for a small firm. Paying early stops the clock; restructuring and deferral are separate applications.

Example 3 — a rate change: 20,000 TL due 1 October 2025, paid 1 January 2026. 1 October⁠–⁠12 November still sits at 4.5%; 13 November⁠–⁠1 January uses 3.7%. Split the calendar, then apply each rate to its own stretch. Multiplying all ninety days by 3.7% understates the October⁠–⁠November piece. On a long debt, open the calendar first, then the rate table.

Late-payment interest vs delay interest

They often share a rate; they are not the same job. Late-payment interest runs until an overdue assessment is paid (Law 6183 Art. 51). Delay interest runs on taxes assessed by amendment, ex officio or by the administration, from the normal due date to assessment (or, if litigated, to service of the court decision) under TPL 112. Partial months: daily for late-payment interest; ignored for delay interest.

Voluntary disclosure also uses the same rate for its interest line. Whether you are looking at “faiz” or “zammı” depends on which line the document opened. Read the assessment slip beside the payment plan.

What the desk looks like when a return is late

VAT is often due on the 28th of the following month. Paying at month-end after missing the 28th still leaves the principal due and adds a few days of interest. “I paid in the same month” does not erase interest once the due date has passed. The withholding and social-security return follows the same logic: the day is on the calendar; interest starts after that day.

A sole prop who reaches the March return without paying provisional tax only credits what was actually paid. Unpaid provisional tax does not vanish into the annual figure; late-payment tracking stays open. That split is also in how provisional tax is calculated. Brackets and late-payment interest are not one box.

A second mix-up in Kızılay files treats special irregularity and late-payment interest as one penalty. Missed e-document sales raise irregularity; that line does not take late-payment interest. Unpaid VAT principal in the same period does. Two lines, two rules.

What should you do?

1. Mark the due day; general dates are in the tax calendar.
2. Note the unpaid amount and due date; estimate interest on the calculator.
3. Pay the principal as soon as you can; interest grows until payment day.
4. In an audit or voluntary-disclosure file, do not mix delay interest with late-payment interest; read the document line.
5. If you consider restructuring or deferral, confirm the deposit, window and conditions separately; deferral interest is not late-payment interest.

Missed e-document rules raise a special irregularity track of their own; that story is in the 1 July 2026 e-Invoice guide. Irregularity penalties do not attract late-payment interest; tax principal and tax-loss penalties can.

Frequently asked questions

What is the 2026 late-payment rate in Turkey?

3.7% per month from 13 November 2025, set by Presidential Decree 10556. If a newer decree is published, the new rate applies to time after that date.

Is late-payment interest calculated daily?

Full months use the monthly rate; partial months are daily. The daily rate is the monthly rate divided by 30. At 3.7% that is about 0.1233% per day.

Is it the same as delay interest?

No. The rate is often the same; the trigger and period differ. Late-payment interest follows overdue payment; delay interest follows the assessment path. Partial months are daily for the former and ignored for the latter.

Does irregularity penalty attract late-payment interest?

No. Article 51 applies the rate to tax-loss penalties under the Tax Procedure Law; it does not apply it to irregularity and similar penalties. Some court-ordered penalty claims use half the rate.

Does it apply to social-security premiums?

Yes, overdue premiums show a late-payment line. Read the period breakdown on the SGK / collection screen. Do not mix it with a tax-debt interest line in the same mental box.

How is an old debt read after a rate change?

Each stretch uses its own rate. Days before 13 November 2025 keep 4.5% (or whatever applied then); days after use 3.7%. Multiplying the whole past by one rate produces the wrong total.

In short

Late-payment interest accrues month by month on overdue public receivables. In 2026 (since 13 November 2025) the monthly rate is 3.7%. Partial months are daily. Delay interest may share the rate, but it belongs to the assessment path and ignores day fractions.

At Ankara Muhasebeci in Kızılay we separate assessment, due date and interest on one desk. For a quick check use the late-interest calculator. To talk through your file, get in touch or see tax advisory. What to bring is on the first-meeting list.

One line: once the due date passes, the clock runs; rates are read period by period; delay interest and late-payment interest are not one box. Paying early stops the interest.