Long after year-end settlement, the realisation arrives: "wait, that was deductible." It feels too late. It isn't — you can reclaim it for up to five years.
The mechanism is called an amended return (경정청구): a formal request to correct an overpayment or an under-refund.
Three lines — ① you have five years from the statutory filing deadline ② you file it yourself, not through your employer ③ approved claims are usually refunded within two months.
1. How far back can you go?
The clock starts at the statutory deadline — March 10 for employment income settlement, May 31 for comprehensive income tax. Five years from there.
| Tax year | Approximate deadline to claim |
| 2021 | Around March 2027 |
| 2022 | Around March 2028 |
| 2023 | Around March 2029 |
| 2024 | Around March 2030 |
| 2025 | Around March 2031 |
So five years are open at once. If you missed the same item every year, the total can be substantial.
You don't need to tell your employer. Many people assume they must ask the company again — but you file directly with the tax office or through Hometax. It works even for a former employer, and nothing is reported back to them.
2. The most commonly missed items
| Item | Why it gets missed |
| Monthly rent credit | Unaware, or avoiding friction with the landlord (requirements) |
| Parents living elsewhere | Assumed ineligible due to different addresses — actual support qualifies |
| Glasses, lenses, hearing aids | Often absent from the pre-filled data |
| Disability deduction | Registration isn't required — serious illness can qualify under tax law |
| Donations | Religious and small donations often unreported |
| SME employment tax reduction | Eligibility unknown to the employee |
| Housing loan deductions | Jeonse loan repayments, mortgage interest |
| Single-parent deduction | Not applied automatically |
⚠️ Worth checking: tax-law disability status. Even without a disability registration card, someone requiring continuous treatment for a serious condition can qualify. A hospital-issued certificate enables the deduction, and it can be claimed retroactively — often one of the largest refunds available.
3. How to file — Hometax handles it
| 1 | Log into Hometax → tax filing → comprehensive income → amended return |
| 2 | Select the year — your original filing loads automatically |
| 3 | Add the missing deductions |
| 4 | Attach supporting documents |
| 5 | Enter your refund account and submit |
| 6 | Review, then refund usually within two months |
If Hometax feels daunting, visiting your district tax office works too — bring ID and documents.
4. If you can't find the paperwork
- Medical — ask the hospital or pharmacy to reissue, or pull treatment records from the health insurance service
- Donations — request a reissued receipt from the organisation
- Rent — lease copy plus bank transfer records
- Education — request a payment certificate from the school
- Glasses — ask the retailer to reissue (annual limit per family member applies)
Most documents can be reissued. Don't give up because years have passed.
5. Other situations that qualify
| Left a job mid-year | Often only basic deductions were applied — refunds are frequently large |
| Changed jobs without combining income | File combined and apply deductions |
| Freelance income never filed | Expense rates can produce a refund (3.3% refunds) |
| Duplicate dependent claims | Fix proactively — duplicates lead to clawbacks |
Mid-year leavers should always check. If you resigned and didn't take another job, the employer likely applied only basic deductions in a simplified settlement — medical, insurance and donation deductions are missing entirely.
6. Cautions
- You must genuinely qualify. Overreaching claims get rejected, or clawed back with penalties.
- Dependent deductions need care — check income limits and whether another family member already claimed them.
- Results take time; the review isn't instant.
- If rejected, objection and appeal procedures exist.
FAQ
Does this affect my employer?
No. It's your personal tax matter and isn't reported to them.
What about a company I've left?
Fine — the payment statement is already with the tax service, so no cooperation is needed.
How much might I get back?
It depends on the item and your income. The rent credit alone, claimed across five years, can reach several million won.
Do I need a tax agent?
For straightforward items, filing yourself is fine. Complex income or large amounts may justify professional help — check the fee first.
An amended return isn't a favour — it's a taxpayer's right. You have five years, so spend thirty minutes reviewing the last five today.
This is general information, not tax advice. Requirements and limits differ by tax year and circumstances — confirm with Hometax or a professional.
