Deadline and Refund Application Process for Year-End Tax Settlement Corrections

If you paid too much income tax because you missed a deduction or tax reduction during year-end tax settlement, you can correct the tax amount by filing a claim for reassessment. However, not all expenses are deductible, and the general right to file a claim expires after the period prescribed by law.

What Is a Claim for Reassessment?

A claim for reassessment is a procedure through which a taxpayer asks the competent tax office to reduce a tax amount that was reported or finalized through year-end tax settlement when it exceeds the correct amount. If the claim is accepted and the tax is reduced, the difference from the amount already paid may be refunded.

Employees should check for the following situations:

• An applicable income deduction or tax credit was omitted during year-end tax settlement
• Supporting documents for a deduction were not submitted to the employer
• An applicable benefit, such as an income tax reduction for employees of small and medium-sized enterprises, was not reflected
• Too much tax was paid because dependent information or expense amounts were entered incorrectly

Conversely, if excessive deductions were claimed and too little tax was paid, the matter may require an amended return or additional payment rather than a claim for reassessment.

When Can You File a Claim?

Under the Framework Act on National Taxes, the general deadline for filing a claim for reassessment is within 5 years after the statutory filing deadline. It is not calculated simply from the day after the tax was paid.

Deductions omitted from an employee’s year-end tax settlement can be reflected in the final comprehensive income tax return filed in May of the following year. If they were not reflected during that period either, a claim for reassessment may be filed after the statutory deadline for the final return has passed.

The table is based on standard employee year-end tax settlement cases. If the final day is a public holiday or an individual filing deadline was extended, the actual deadline may differ, so it should be confirmed through Hometax or the competent tax office.

For the 2020 tax year, the standard 5-year period for filing a claim for reassessment ended in 2026. This does not mean that a refund was automatically created and then disappeared; it means that the period for exercising the standard right to file a claim for reassessment has ended.

If a subsequent statutory event, such as the finalization of a court judgment or cancellation of a transaction, occurred later, a separate claim period may apply. A subsequent-event claim for reassessment is not recognized merely because the taxpayer learned about a deduction belatedly.

Easily Overlooked Deductions and Tax Reductions

Monthly Rent Tax Credit

The monthly rent tax credit is not an item for which the lease agreement and bank transfer records are automatically reflected in full. The statutory requirements for the relevant tax year must be met, including the no-homeownership requirement, total salary threshold, housing requirements, and registered residential address.

The documents generally prepared include:

• Resident registration certificate
• Copy of the lease agreement
• Proof of monthly rent payments, such as bank transfer receipts or deposit slips

The credit may be restricted if rent was paid in cash without objective proof of payment or if the relationship between the contracting party and resident does not meet the requirements.

Medical Expense Tax Credit

You can check whether any medical expenses were omitted from the simplified year-end tax settlement data. However, not all non-covered medical expenses that are not covered by health insurance are deductible. Expenses for cosmetic or plastic surgery purposes and purchases of medicines for health promotion may be excluded from the credit.

For medical expenses not included in the simplified data, documents such as receipts issued by medical institutions are required to verify the expense details and eligibility for the credit.

Donation Tax Credit

Donations must have been made to an organization eligible for a deduction under tax law. The mere fact that a receipt was issued by a religious or private organization does not guarantee the credit, so the organization’s eligibility and the type of donation must be verified.

Income Tax Reduction for Employees of Small and Medium-Sized Enterprises

Young people, older adults, persons with disabilities, women returning to work after a career interruption, and other statutorily eligible individuals may receive an employment income tax reduction if they obtain employment at a qualifying small or medium-sized enterprise. Eligibility and the applicable period vary depending on the employment date, employee category, the company’s industry, and whether the company qualifies as a small or medium-sized enterprise.

Generally, the employee submits a tax reduction application to the employer, and the employer submits a statement to the tax office. If the reduction was not applied at the time, the possibility of filing a claim for reassessment can be reviewed after confirming the eligibility requirements with the employer.

Marriage-Related Tax Credits

The same tax reduction does not apply to every year merely because a couple is newly married. For programs with limited application periods, such as the marriage tax credit, the date of marriage registration and the statutory requirements for the relevant tax year must be reviewed.

How to File a Claim for Reassessment Through Hometax

1. Log in to Hometax.
2. Under Tax Filing, go to the Comprehensive Income Tax Return menu.
3. Select Claim for Reassessment under Employment Income Return.
4. Load the tax year for which you are filing and the existing year-end tax settlement details.
5. Correct the omitted income deduction, tax credit, or tax reduction items.
6. Submit supporting documents proving that the deduction requirements are met.
7. Check the calculated tax amount and refund account, then submit the return.
8. Save the filing receipt and a copy of the return, and check the processing status.

If the relevant tax year does not appear in Hometax or electronic filing is difficult, you can ask about preparing a return and submitting it to the competent tax office.

Documents to Prepare Before Filing

Because credit rates, limits, and eligibility requirements may be revised, you must apply the tax law for the tax year covered by the claim for reassessment, not the current rules.

Processing After Filing and Precautions

A claim for reassessment is a procedure for requesting a refund, not one that immediately finalizes a refund. After reviewing the claim and supporting documents, the tax office either adjusts the tax amount or notifies the taxpayer that there are no grounds for the claim. Under the Framework Act on National Taxes, the tax office is generally required to notify the taxpayer of the result within 2 months from the date the claim is received.

The following should also be checked:

• The claim may not be accepted if it includes expenses that are not eligible for a deduction.
• The refund is not the full amount of the omitted expense but the reduction in tax resulting from recalculating the deduction.
• The refund may be smaller than expected because of restrictions on combining deductions or deduction limits.
• Check that multiple family members have not claimed the same dependent deduction.
• The local income tax refund procedure and timing may differ from those for income tax.

If the deadline is approaching, it is advisable to review the supporting documents first and confirm whether filing through Hometax is available or how to submit the claim to the competent tax office.