Korean capital gains tax is filed on an interim return after each sale and settled with a final return after the year ends. Income Tax Act Article 110 requires residents with capital gains to file from 1 to 31 May of the following year, even with no tax base or a loss. But if you filed interim returns, you may skip the final return (para. 4), except where, for example, you filed two or more interim returns on progressively-taxed assets in the same year. For foreign shares, which have no interim return, the final return is the first filing.
1. Final return: 1–31 May next year — even at a loss.
2. Interim return filed? Usually you can skip it (Art. 110(4)).
3. Exception: two or more interim returns on progressive-rate assets, etc. — recomputed together.
The article — Art. 110
| Type | What the source says | Worth noting (ours) |
|---|---|---|
| (1) | Residents with capital gains file 1–31 May of the following year; permit-zone cases use the year of the permit (or release) | — |
| (2) | Applies even with no base or a loss | File losses too |
| (3) | This is the “final return” | — |
| (4) | Those who filed interim returns may skip it, except where, e.g., they filed two or more interim returns on progressive-rate assets in the year (Decree) | Rest of the list in the Decree |
| (5)–(6) | Attach proof of sale price and expenses; the office may ask for corrections | — |
Who files again in May — our summary
| Situation (our example) | May final return | Worth noting (ours) |
|---|---|---|
| Sold one flat in 2026, filed interim | Can skip | Para. 4 main rule |
| Sold land twice in 2026, two interim returns | Must file | Two+ interim returns on progressive assets |
| Sold only US shares in 2026 | Must file (May 2027) | No interim return; this is the first |
| No interim return filed | Must file | Late interim return penalties — see the calculator |
Two sales of progressive-rate assets are taxed separately on interim returns but may reach a higher band combined; the final return recomputes them together (our reading), which can mean more tax.
What and when for a 2026 sale — our summary
Sell a flat on 20 October 2026 and the interim return is due by 31 December 2026; with a second property sale and interim return the same year, the final return is 1–31 May 2027. Foreign share sales go straight to May 2027. Interim deadlines are in capital gains interim return deadline calculator; foreign shares in overseas stock capital gains calculator.
If 31 May is a weekend — Framework Act Art. 5
Deadlines on a Saturday, Sunday, public or substitute holiday or Labour Day move to the next day; 31 May 2027 is a Monday, so it stands (our check). The final return attaches proof of the sale price and expenses, and the office may ask for corrections (Art. 110(5)–(6)). Tax paid with interim returns reads as credited against the final figure, but we didn’t read that settlement article.
Checklist
- ☐ List this year’s sales and interim returns
- ☐ Two+ progressive-rate assets: file in May
- ☐ Foreign shares: first filing in May
- ☐ File even at a loss
- ☐ Proof of price and expenses
Questions that remain
What else is in the “etc.”?
Para. 4 defers to the Decree, which we didn’t read; check Hometax or the tax office.
Can losses offset gains?
We didn’t read the loss-offset article (Art. 102).
Sources
- Korean law database (law.go.kr) — Income Tax Act Arts. 105, 110 — source (current text, effective 1 July 2026, Act No. 21221; checked 20 October 2026). Final return in May, permit-zone proviso, applies at a loss, skipping after interim returns and the two-return exception, documents and corrections.
- Korean law database — Framework Act on National Taxes Art. 5 — source (effective 2 October 2026; checked 20 October 2026). Weekend and holiday deadlines.
- Not read. The Decree list under Art. 110(4); loss offsetting (Art. 102); crediting interim payments.
- What we added. The “worth noting” column and the Korean everyday gloss.
Where to check further
- NTS Hometax — final-return guidance.
Written on 20 October 2026. The content is from the source; the glosses are ours.
