Month End Starts Korea's Inheritance Tax Clock. The Date of Death Does Not.

The Scene

An heir in Ohio learns that her father died in Seoul on 3 March. Within a week she has found four English-language summaries of Korean inheritance tax, and all four say the same thing: the return is due six months after death. She writes 3 September on the calendar, blocks out August for the paperwork, and stops worrying about the date.

The date is wrong, and it is wrong in the direction that rarely causes trouble. The Inheritance Tax and Gift Tax Act (상속세 및 증여세법) does not count six months from the day the inheritance commenced. It counts six months from the last day of the month in which the inheritance commenced. For a death on 3 March the clock starts on 31 March, and the return is due 30 September — twenty-seven days later than the calendar she drew up.

The same construction governs gift tax in the next article, with three months instead of six. Neither article measures from the event. Both measure from the end of the event's month, which produces two consequences at once: the deadline in each example worked below falls on the last day of a month, and two people whose events fell thirty days apart can share a single due date.

That is a small drafting choice with a large practical footprint, and it is the part that English summaries compress away. The version of the Act referred to throughout is the one whose header appears at the top of each linked page: [시행 2025. 10. 1.] [법률 제21065호, 2025. 10. 1., 타법개정].

What the Rule Actually Says

The anchor sits in paragraph 1 of Article 67

Article 67 (상속세 과세표준신고) opens by naming who files and then, before it names any period, names the point the period runs from. The operative words are “상속개시일이 속하는 달의 말일부터 6개월 이내에” — within six months from the last day of the month to which the date of commencement of the inheritance belongs. The filing goes to the head of the tax office having jurisdiction over the place of tax payment, and the paragraph covers both the taxable value and the tax base.

The duty itself is not created here. Paragraph 1 conditions on a person having the obligation to pay under Article 3-2, which places the liability on heirs and legatees in a ratio prescribed by Presidential Decree, computed on the basis of the property each received or is to receive. The parallel gift-tax duty sits in Article 4-2. Both are on the National Law Information Center page for Articles 3-2 and 4-2, which displays those two articles and no others.

Paragraph 4 changes the number, not the anchor

The nine-month figure that appears in guides for foreign heirs is paragraph 4 of the same article, and it is one sentence long: “피상속인이나 상속인이 외국에 주소를 둔 경우에는 제1항의 기간을 9개월로 한다.” It replaces the period in paragraph 1 and leaves everything else in paragraph 1 standing, including the month-end anchor. The 3 March death therefore runs to 31 December rather than to 30 September.

Two words in that sentence do more work than the number does. The condition is 주소 — an address, in the sense the tax law uses for where a person is domiciled — and not citizenship, so a Korean national living abroad and a foreign national living in Korea sit on opposite sides of it from where a nationality test would put them. And the sentence reads 피상속인이나 상속인이, the decedent or an heir, without the word 전원 that Korean drafting uses when it means every member of a group. English summaries that render this as “the decedent or all of the heirs” are adding a qualifier the displayed text does not contain. Whether a given person's 주소 is abroad is a question of fact rather than of paperwork, and that is where the argument in a real case tends to be.

Gift returns run on three months, with a proviso

Article 68 (증여세 과세표준신고) uses the identical construction: “증여받은 날이 속하는 달의 말일부터 3개월 이내에”. A gift received on 5 January is not due on 5 April. Its month ends 31 January, and the return is due 30 April.

The proviso that follows carries two different anchors for cases where there is no single moment of receipt to count from. For the listing of unlisted stock under Article 41-3 and for corporate mergers under Article 41-5, the settlement return is due three months from the last day of the month containing the settlement reference date. For Articles 45-3 and 45-5, the deadline is three months from the last day of the month in which the corporation's own corporate tax return deadline under Article 60, paragraph 1 of the Corporate Tax Act falls. Both articles are on the National Law Information Center page for Articles 67 and 68, which displays those two articles in full.

Two further clocks live inside Article 67

Paragraph 3 moves the starting point for an executor of a will or an administrator of the estate: the period is counted from the day that person is designated or appointed, and only where the designation or appointment happens inside the paragraph 1 period. Paragraph 5 adds a separate obligation with its own short period. Where the heirs are not determined by the paragraph 1 deadline, the statute requires, separately from the paragraph 1 return, a submission to the same tax office within thirty days of the day the heirs are determined, setting out the inheritance relationships of the heirs so determined. It is a filing about who the heirs are, not a second tax return, and it exists precisely because the main deadline can arrive before that question is settled.

The Numbers

Because the anchor is a month end rather than a date, the real length of the six-month window depends on where in the month the death fell, and the spread is a full month wide. A death on 1 March and a death on 31 March both start their clock on 31 March and both produce a 30 September deadline. The first heir has 213 days. The second has 183. The 3 March death in the opening has 211 days, twenty-seven more than the 184 that a count from the date of death would have produced. On the gift side the same effect is smaller but identical in shape: a gift received on 5 January is due 30 April, which is 115 days rather than the 90 days a count from the date of receipt would give, a difference of 25 days.

For scale, the National Tax Service publishes the standing stock of cases these deadlines govern. Its national tax statistics, presented through the e-Nara indicator for inheritance and gift tax determinations and attributed to the NTS inheritance and gift tax division with a refresh date of 7 July 2026, record 22,524 persons subject to inheritance tax in 2025 against a determined amount of 89,345 in units of a hundred million won, and 181,653 gift tax cases against 54,828 in the same units. The inheritance figure rose by 1,331 persons year on year; the gift tax amount fell by 1,984 of those units.

Those inheritance numbers are small relative to the population of estates. The most recent year published on the e-Nara indicator for mortality by cause of death, sourced to the national data agency's cause-of-death statistics and refreshed 14 July 2026, is 2024, with 358,569 deaths and a crude death rate of 702.6 per hundred thousand. The tax series runs a year further forward than the mortality series, so the two cannot be divided cleanly, but the order of magnitude holds: taxable persons number in the tens of thousands against deaths in the hundreds of thousands, on the order of one in sixteen. The deadline in Article 67 is not a deadline that most estates end up owing anything against, which is a separate matter from whether the period ran.

One more number sits downstream of the deadline. Article 69 (신고세액 공제) grants a credit of three one-hundredths — three percent — where the tax base has been reported under Article 67 or Article 68. The three percent is not taken on the headline tax. Paragraph 1 computes it on the calculated inheritance tax, including any amount added under Article 27, less two things: amounts whose collection has been deferred under Article 74, and amounts credited or reduced under this Act or another Act. Paragraph 2 does the same for gift tax, reading Article 57 for the addition and Article 75 for the deferral. On a calculated tax of 100 million won with no deferrals and no other credits, the arithmetic is straightforward and the credit is 3 million won; introduce either subtraction and it is less than that.

Where This Doesn't Apply

Article 68 has no nine-month paragraph. The extension for an address abroad is drafted into Article 67, and the text of Article 68 displayed alongside it contains no equivalent. A gift received by a donee living outside Korea still runs on three months from month end, and the symmetry that readers expect between the two returns stops here.

The proviso cases do not use the event month at all. Where Article 41-3, Article 41-5, Article 45-3 or Article 45-5 applies, the month that matters is the one containing the settlement reference date or the corporate tax return deadline, not the month of any transfer. Reading the main clause and stopping there produces the wrong month in exactly the cases where the amounts are largest.

Paragraph 3 can move the start for an estate under administration. For an executor or an administrator, the count begins at designation or appointment, and the paragraph limits that to designations and appointments falling inside the paragraph 1 period. An estate handled through a representative is not automatically on the same clock as the heirs.

The thirty-day paragraph is not a deadline extension. Paragraph 5 sits alongside the paragraph 1 return rather than in place of it. The main period does not pause because the heirs are still being identified.

The Act ties the credit to the return, not to its timeliness. Article 69 conditions on the tax base having been reported under Article 67 or Article 68. The text displayed on the statute page does not itself say what becomes of the credit when the return arrives after the period has run, and no conclusion about that should be drawn from the words quoted here. The consequences of a late or missing return are set by other provisions and other statutes.

Other statutes keep their own clocks. Article 67 fixes when the inheritance tax return is due. It does not govern the deadlines that other Acts attach to a death or a transfer, and those run on their own terms regardless of what this one says.

If You Are Actually in This Situation

The first step is a calendar step rather than a tax step, and it is the one the English summaries skip. Write down the month in which the death or the gift occurred, take the last day of that month, and count from there. Six months for an inheritance return under Article 67, three for a gift return under Article 68. Because the count starts at a month end, the deadline in each example worked above is also a month end. Exactly which day a period expires on is settled by the general rules on counting statutory periods, which Article 67 does not contain and which are not quoted here.

Then check whether paragraph 4 is in play, and check it on the right test. It asks where the decedent or an heir has an address, not what passport anyone holds, and the displayed sentence does not require that every heir be abroad. If the answer changes the number to nine, the anchor does not move with it; only the number does.

Separately, note whether the heirs are settled. If they are not going to be settled by the paragraph 1 deadline, paragraph 5 puts a thirty-day obligation on the far side of the day they are determined, and it runs from that day rather than from any month end. It is the one period in this group that is counted the way most readers assumed all of them were.

The payment side rides on whatever date the count produced. Article 70 requires the calculated tax, less the amounts that article lists, to be paid by the same filing deadline, and its paragraph 2 allows part of an amount over 10 million won to be split and paid within two months after that deadline, except where annual instalments have been authorised under Article 71. The text of both articles is on the National Law Information Center page for Articles 69 and 70, which displays those two articles and no others.

Two earlier footnotes on this blog sit underneath this one. The ten-year window that decides how much of a transfer is deductible is described in the piece on Korea's per-donor ten-year gift total, and the rate structure that produces the calculated tax the three percent is taken on is set out in the piece on what the inheritance tax table actually contains. The deadline article decides when; those two decide how much.

Everything above describes what the cited provisions say as displayed on the National Law Information Center pages linked in each section, on the version headed 법률 제21065호. Which provision applies to a particular estate or transfer, and whether a person's address falls inside or outside Article 67, paragraph 4, are determinations made on the facts of the case by the tax office or by a licensed professional, and nothing here is tax or legal advice.