Amended Return Refund Calculator (5-Year Retroactive)

What is an amended-return (경정청구) refund?

A claim for correction, called 경정청구 in Korean, is the procedure for recovering national tax you overpaid because you reported more than you actually owed.
Under Article 45-2 of the Framework Act on National Taxes, a taxpayer who filed by the statutory due date may ask the tax office to correct the tax base and amount within 5 years after that due date.

This calculator estimates three things at once: the refund principal (the overpaid tax), the statutory refund interest added on top (국세환급가산금), and the 5-year claim deadline by tax type and tax year.
It is most useful for recovering missed year-end settlement or global income deductions (medical expenses, monthly rent, donations, pension accounts), missed VAT input tax credits, or plain calculation errors.

Korea-based, 2026 rules. This calculator reflects the Framework Act on National Taxes Article 45-2 (5-year claim), Article 52 and Enforcement Decree Article 43-3 (refund interest, accrual from the day after payment), and Enforcement Rule Article 19-3 (annual rate of 3.1% for 2026). It is a reference estimate for Korean national tax and does not replace professional filing advice.

How the refund is built

1. Refund principal (overpaid tax)

The refund principal is the tax you actually overpaid — the originally reported and paid tax minus the correct tax after applying the deductions or credits you missed.
For example, if you paid KRW 5,000,000 of global income tax but the correct figure after deductions is KRW 3,500,000, the refund principal is KRW 1,500,000.

Refund principal formula

Refund principal = originally paid tax − correct tax

2. Statutory refund interest (국세환급가산금)

When tax is refunded through an amended-return claim, the National Tax Service adds statutory interest, not just the principal.
Under Article 52 and Enforcement Decree Article 43-3, the interest accrues from the day after the tax was paid until the refund decision date.
The 2026 rate under Enforcement Rule Article 19-3 is 3.1% per year (31 per 1,000).

Refund interest formula

Interest = refund principal × 3.1% × interest days ÷ 365

The rate is revised each year to track average bank term-deposit rates, so past periods legally use their own rates.
This calculator applies the current 2026 rate across the whole period as a simplified estimate, and flags that in the result.

3. Total expected refund

The final amount you receive is the refund principal plus the refund interest.
The longer the gap between the payment date and the refund decision date, the larger the interest, so older years carry a bigger interest share.

The 5-year retroactive claim window

An amended-return claim is allowed only within 5 years after the statutory filing due date.
The clock starts from the statutory due date of that tax, not from the payment date, so knowing the tax type and tax year lets you pinpoint the last claimable day.

Statutory due date by tax type (by tax year Y)

• Global income tax: May 31 of year Y+1 (e.g., 2022 tax year → 2023-05-31).
• Year-end settlement (wage income): based on the global income final-return due date, May 31 of Y+1.
• VAT: based on the second-period final-return due date, January 25 of Y+1.
• Capital gains tax: final-return due date, May 31 of Y+1.
• Corporate tax (December year-end): March 31 of Y+1.

The claim deadline is that statutory due date plus 5 years.
So 2022 global income tax can be claimed until 2028-05-31.

Even if the ordinary 5-year window has passed, a later-arising cause — a court judgment or a mutual agreement under a tax treaty — allows a claim within 3 months of learning of that cause (Article 45-2(2)).
After a claim is filed, the tax office must notify its decision or refusal within 2 months (Article 45-2(3)).

How to use the calculator

Step 1: Choose tax type and tax year

Pick the tax (global income, year-end settlement, VAT, capital gains, or corporate) and the year the tax belongs to; the matching statutory due date is shown automatically.

Step 2: Enter the refund amount

Enter the originally paid tax and the correct tax to get the difference as the refund principal, or switch to direct-input mode if you already know the refund amount.

Step 3: Enter the payment and refund dates

Enter the date the tax was paid and the expected refund decision date; the interest period is computed from the day after payment. The refund date defaults to today.

Step 4: Review the result

See the total expected refund, the interest breakdown, the 5-year deadline with a claimable/expired badge, and a table of recent tax years with days remaining.

Frequently asked questions

Q. How far back can I claim?

A. Within 5 years after the statutory filing due date.
Because the last claimable day depends on tax type and tax year, use the table to check each year for expiry.

Q. Do I also receive interest?

A. Yes. Tax refunded through an amended-return claim carries statutory refund interest (Article 52).
The 2026 rate is 3.1% per year, accruing from the day after payment to the refund decision date.

Q. Where do I file?

A. Online through Hometax (hometax.go.kr) or in writing at your competent tax office.
The office notifies its decision within 2 months.

Q. Is it hopeless once 5 years pass?

A. Ordinary claims are limited to 5 years, but a later-arising cause (a court judgment or treaty mutual agreement) allows a claim within 3 months of learning of it.
These depend on the specific facts, so consult a professional.

Cautions

• This is an estimate under the 2026 Framework Act on National Taxes and its subordinate rules; the actual refund depends on the tax office’s review.
• The interest uses the current 3.1% rate across the whole period, while the law applies each period’s own rate.
• VAT and capital gains tax due dates can differ by filing type and taxable period.
• If the claim is accepted, related taxes such as local income tax may also be adjusted.
• File accurately through Hometax or a tax professional.

Tax scenario inputs

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