When you overpaid tax or win a refund claim, the Korean tax office adds national tax refund interest to the money it returns. Article 52 of the Framework Act on National Taxes adds interest for the period from the start date set by decree to the day of the offset or the payment decision, and Enforcement Rule Article 19-3 sets the rate at 31/1,000 a year (3.1%). The start date depends on why the refund arose: the day after payment for mistaken payments and corrections, and the day after 30 days have passed for refunds on a return or application. Paid 40 days or more after an appeal ruling becomes final, the rate is 1.5 times. Enter the amount and dates to work out the interest.
1. Refund interest is 3.1% a year (Rule Art. 19-3, 31/1,000).
2. Mistaken or double payments and corrections: from the day after payment to the payment decision (Decree Art. 43-3(1)1).
3. Paid 40 days or more after an appeal ruling became final: 1.5 times; refunds via a grievance get none.
Calculator
Updates as you type. Days run from the start date through the payment (or offset) decision date, both included. Interest = refund × rate × days ÷ 365, rounded down to the won (our method). One current rate is applied to the whole period; where the rate changed during it, the transitional rules were not read.
The articles
| Type | What the source says | Worth noting (ours) |
|---|---|---|
| Framework Act Art. 51(1) | Where tax was paid by mistake or in excess, or a refund is due under a tax law, the office immediately decides it as a national tax refund | — |
| Art. 52(1), (2) | On offsetting or paying a refund, interest is added for the period from the start date to the offset date or the payment decision date at the decreed rate. For an Art. 51(8) offset, to the payment decision date | The end is the decision date, not the day the money lands |
| Art. 52(3) | Refunds offset or paid through a grievance without a refund claim (Art. 45-2) or an appeal ruling get no interest | A refund claim does carry interest |
| Decree Art. 43-3(2) | The basic rate is set by ministry rule considering banks’ average one-year deposit rates. Paid 40 days or more after an appeal decision or ruling became final: 1.5 times the basic rate | The 1.5x proviso dates from 30 Dec 2025 |
| Rule Art. 19-3 | The rate is 31/1,000 a year | No rate change in the amendments since 21 Mar 2025 |
| Art. 54 | Rights to refunds and refund interest lapse after 5 years from when they could be exercised; a tax office reminder does not interrupt this | — |
When interest starts — Decree Art. 43-3(1)
The decree makes the start date the day after these dates:
| Why the refund arose | Base date | Worth noting (ours) |
|---|---|---|
| Mistaken or double payment; correction or cancellation after payment | Payment date | Split payments count back from the last one. Interim prepayments and withheld tax count as paid on the statutory filing deadline of that tax |
| Reduction of lawfully paid tax | Reduction decision date | — |
| Refund after a law change | Effective date of the amended law | — |
| Refund on a return, application, correction or decision under the Income Tax Act etc. | 30 days after filing (the statutory date if filed early) or applying | Where a tax law sets a refund deadline, the day after it. The calculator treats filing date + 30 as “the day 30 days have passed” and starts the next day (our reading) |
For an employee with only year-end settlement who wins a refund claim, withheld tax counts as paid on the income tax filing deadline (31 May of the next year), so on our reading interest starts on 1 June. In the calculator, choose “correction” and enter 31 May as the payment date. How long you have to claim is in the tax refund claim deadline calculator.
Three sums — our examples
| Case (our example) | Start · days · interest | Worth noting (ours) |
|---|---|---|
| ₩1,000,000 paid by mistake (29 May 2026), decided 27 Oct | 30 May · 151 days · ₩12,824 | Our sum: 1,000,000 × 3.1% × 151 ÷ 365, rounded down |
| ₩2,000,000 refund return (1 June 2026), decided 10 Aug | 2 July · 40 days · ₩6,794 | From the day after 1 July, when 30 days have passed |
| ₩10,000,000 correction (paid 31 May 2024), decided 27 Oct 2026 | 1 June 2024 · 879 days · ₩746,547 | After an appeal win paid 40+ days late: ₩1,119,821 at 1.5x |
The third example applies today’s 3.1% to the whole period from June 2024. If the rate changed in between, the real figure may differ; we didn’t read the transitional rules on splitting periods.
Checklist
- ☐ Why the refund arose (mistake/correction, reduction, law change, return/application)
- ☐ The end date is the payment decision (or offset) date
- ☐ Appeal won and paid 40+ days after it became final: 1.5x
- ☐ Grievance alone: no interest
- ☐ Unclaimed refunds lapse after 5 years
Questions that remain
Is the interest taxed?
The articles we read only say how it is counted; we didn’t read whether it is taxed.
How do I find an unclaimed refund?
See finding unclaimed national tax refunds. The right lapses 5 years after it could be exercised (Art. 54).
Is it the same for local tax refunds?
Local taxes have their own framework act, which we didn’t read.
Sources
- Korean law database (law.go.kr) — Framework Act on National Taxes Arts. 51, 52 and 54 — source (current text, effective 2 October 2026, Act No. 21987; checked 27 October 2026). Refund decisions (immediately), refund interest (start date to offset or decision date), no interest for grievances and its exceptions, the 5-year lapse and reminders not interrupting it.
- Korean law database — Enforcement Decree Art. 43-3 — source (effective 1 July 2026, Decree No. 36125; checked 27 October 2026). The four start dates, basic rate and 1.5x, grievances.
- Korean law database — Enforcement Rule Art. 19-3 — source (effective 20 March 2026, Ministry Ordinance No. 18; checked 27 October 2026). 31/1,000 a year.
- Not read. Offset order details in Art. 51, the Rule’s transitional provisions on rate changes, taxation of the interest, local tax refund interest.
- What we added. The “worth noting” column and the Korean everyday gloss.
Where to check further
- Your tax office — the decision date, and periods spanning a rate change.
Written on 27 October 2026. The content is from the source; the glosses are ours.
