There is a reason the standard Korean apartment is 84㎡. Cross 85㎡ of exclusive floor area and the tax notice gains a line — the special rural development surtax. On a KRW 900m home that is 1.8m won; under the 12% heavy rate, 9m.
85㎡ or less is exempt. Over it, the surtax applies — 0.2% at standard rates, 0.6% under the 8% heavy rate, 1.0% under 12%.
The formula is not the acquisition rate but “10% of the acquisition tax computed at 2%” (Rural Special Surtax Act art. 5(1)6). Under a heavy rate, the amount the heavy rate added goes on top of that 2% — 4 points at 8%, 8 points at 12%.
Applying 10% to the whole acquisition rate is wrong — that gives 0.8% and 1.2%, where the right answers are 0.6% and 1.0%.
What 0.1㎡ is worth
84.9㎡ against 85.1㎡. Same rate, different area.
| Price | One home (0.2%) | 8% heavy (0.6%) | 12% heavy (1.0%) |
|---|---|---|---|
| KRW 500m | 1m | 3m | 5m |
| KRW 900m | 1.8m | 5.4m | 9m |
| KRW 1.2bn | 2.4m | 7.2m | 12m |
Acquisition tax and education tax do not look at floor area at all. This is the only line that does. So at the same price, 84㎡ and 85.1㎡ produce different notices.
Why 2% rather than the actual rate
The surtax rides on the acquisition tax but does not follow the acquisition rate. The statute fixes it at “10% of the tax computed at 2%.”
| Acquisition rate | Base for the surtax | Surtax rate |
|---|---|---|
| 1% (one home, up to 600m) | 2% | 0.2% |
| 2.33% (one home, 800m) | 2% | 0.2% |
| 3% (one home, over 900m) | 2% | 0.2% |
| 8% (heavy) | 2% + 4 points | 0.6% |
| 12% (heavy) | 2% + 8 points | 1.0% |
Look at the middle three rows. The acquisition rate triples from 1% to 3% and the surtax stays fixed at 0.2%. “It is a surtax, so it must be proportional to the main tax” breaks here.
Only the heavy rates change it, and even then it is not the whole rate but the amount the heavy rate added that goes on top of the 2%. Multiplying 8% by 10% gives 0.8%, and that is the wrong figure.
The reason shows in how the heavy rate is written. Local Tax Act art. 13-2(1) does not say “8%”; it says “the rate in art. 11(1)7(b) [4%] as the standard rate, plus 200% of the heavy base rate [2%].” So 8% is a 4% standard plus a 4-point add-on. The Rural Surtax Act then says only “applying the standard rate as 2/100” — it swaps out the 4% alone, and the 4-point add-on stays. The base becomes 6%, and a tenth of that is 0.6%.
The education tax moves the other way
The two surtaxes on the same notice behave differently.
| Local education tax | Rural development surtax | |
|---|---|---|
| Floor area | ignored | over 85㎡ only |
| Standard band | tracks the rate (0.1–0.3%) | fixed at 0.2% |
| Heavy 8% · 12% | fixed at 0.4% | splits 0.6% · 1.0% |
| Source | Local Tax Act art. 151 | Rural Surtax Act art. 5(1)6 |
In the standard band the education tax tracks and the rural surtax is fixed; under the heavy rates the education tax is fixed and the rural surtax splits. Exactly inverted. Bundling both as “the surtaxes” hides that structure.
Where the 85㎡ actually comes from
The number 85㎡ appears nowhere in the Rural Surtax Act. It takes three provisions to reach it.
The bottom box is what this article left open for a long time. Housing Act art. 2(6) sets 85㎡ of residential floor area per house or household, and adds the exception in brackets — “for an eup or myeon area that is not an urban area, outside the capital region as defined in the Seoul Metropolitan Area Readjustment Planning Act art. 2(1), 100㎡ or less.”
That is three conditions, all required. Shortening it to “an eup or myeon outside the capital region gets 100㎡” drops the urban-area test — an eup or myeon designated as an urban area stays at 85. This article had been shortening it that way.
Two more details. For a multi-household house the area is measured per household (bracket in Decree art. 4(5)). And the Housing Act leaves how residential floor area is measured to Ministry of Land rules (art. 2(6), second sentence). We opened those rules on 18 September 2026 — a new section follows.
How it is measured: Housing Act Enforcement Rule art. 2
The earlier version said in two places that we did not follow this through. We did — Enforcement Rule of the Housing Act art. 2 (calculation of residential floor area), amended 2 April 2018. The answer we were looking for is not in it.
What the rule settles is which line you measure from, and what you subtract. There is no sentence about decimals — no rounding rule, no truncation rule.
| Type | Measured from | Subtract |
|---|---|---|
| Detached house | Floor area (Building Act Decree art. 119(1)3) | Basement (except space used as living rooms) · storage, garage and toilet detached from the main building |
| Multi-household house | As above, with a proviso | Plus above-ground corridors, stairs and entrances shared by two or more households |
| Apartment | The inner line of the outer wall | Above-ground common area (corridors, stairs, entrances) · basement, management office and other common area |
For an apartment the phrase that matters is "the inner line of the outer wall" — not the centre of the wall, not its outer face. And the rule adds that the outer-wall area left over is added to the common area: the space the wall occupies leaves the exclusive figure and joins the shared one.
So the rule does not decide 85.00 against 85.01. It fixes the method and says nothing about where the decimal is cut. That question still goes to the local authority — the earlier advice stands. What was wrong was saying the answer lay in those rules.
Questions that remain
How big is an 84㎡ apartment exactly?
It varies by development. An “84㎡ type” is registered as 84.87㎡, 84.96㎡ and so on — always 84-point-something, designed not to cross 85. That is the design. Do not confuse it with supply area — a unit sold as 112㎡ is commonly 84㎡ exclusive. The test is exclusive area.
What about exactly 85㎡?
The charge applies above 85㎡, so exactly 85 is exempt, and the calculator treats it that way. How residential floor area is measured is settled by Enforcement Rule art. 2 — for an apartment, from the inner line of the outer wall. Where the decimal is cut is not in that rule either, so if a property sits between 85.00 and 85.01, ask the local authority first.
I heard the threshold differs outside the capital region.
It does, and the exception does carry into this exemption — because the exemption borrows the national housing size wholesale (Decree art. 4(5) to Housing Act art. 2(6)). But all three conditions are needed: (1) outside the capital region, (2) not an urban area, and (3) an eup or myeon. This article used to omit the second; it is corrected above under “Where the 85㎡ actually comes from”. Whether an address sits in an urban area is shown on the land-use plan certificate — worth one check, given the sums.
Does the 85㎡ test apply to officetels?
An officetel is described as taxed at 4% as non-residential property rather than as a home, so the whole rate structure differs and this table cannot be transferred to it. A residential officetel splits two ways (statute checked 23 September 2026). (1) Rate — the housing rates in Local Tax Act art. 11(1)(viii) apply only to buildings recorded as housing in the building register or land registry, so an officetel on the register stays at item (vii)(b), 40 per thousand, even when lived in. (2) Home count — art. 13-3(iv) adds “an officetel taxed as housing under art. 105” to the owner’s number of homes. So it is bought at 4% but can count as a home when you buy the next one. How the surtax exemption’s national-housing-size test reaches officetels we did not examine.
When is the rural surtax paid?
With the acquisition tax. There is no separate notice; it appears as a line on the same one. So when the acquisition tax “seems higher than expected,” what is usually being read is the total with this and the education tax included. The calculator separates all three.
Sources and where to check
National Law Information Center — statutory text — Local Tax Act art. 11(1) (item (vii)(b) 4%; item (viii) defines housing) and art. 13-3(iv) (officetels taxed as housing count as homes). Checked 23 September 2026 (Korean).
Rural Special Surtax Act art. 5(1), item 6 of the table — 10% of “the acquisition tax computed under the Local Tax Act and the tax-relief acts applying the standard rate in arts. 11 and 12 of the Local Tax Act as 2/100.”
Rural Surtax Act art. 4(9) → Decree art. 4(5) → Housing Act art. 2(6) — what the statute exempts is “low-cost housing as prescribed by Decree”; the Decree sets that at national housing size or less (per household for a multi-household house); and the 85㎡ with its 100㎡ exception comes from the Housing Act.
Local Tax Act art. 13-2(1) — the heavy rate is written as “the rate in art. 11(1)7(b) as the standard rate, plus 200% (or 400%) of the heavy base rate.” That form is the reason for 0.6% and 1.0%.
Local Tax Act art. 151 — local education tax: (standard rate × 50%) × 20% for a home purchase, 0.4% under the heavy rates.
On 11 September 2026 all four provisions above were opened on the national law portal and compared. This article had said the statute could not be opened and that a re-check was owed; that debt is now settled. The rates (0.2%, 0.6%, 1.0%) and the formula held. One thing was wrong and has been fixed — the 100㎡ exception was missing its not-an-urban-area condition.
This site’s acquisition tax guide left the rural surtax blank as “a separate act, so the rate is not copied here” — this article fills that gap. The art. 5(1) table sits on the page as an image, so reading the text does not reach it; the alt text carried the provision verbatim, which is how it was transcribed — the same route used for the formula in the slope band.
On 18 September 2026 the Housing Act Enforcement Rule art. 2 — left “unopened” in two places — was opened. The method is confirmed: for an apartment, the inner line of the outer wall, with the leftover wall area going to the common area. But the decimal is not addressed in that rule either. Saying the answer lay in those rules was wrong guidance, and it has been corrected. Short of asking the local authority, this one does not close on the text.
Where to check further
The exclusive area on the register or the contract. Not the supply area. It is written to the decimal.
The Wetax acquisition tax calculator. The safest check on the actual assessment.
For an eup or myeon area, check the urban-area designation first. It is on the land-use plan certificate — an urban area does not get the 100㎡ exception.
The local authority, if the decimals matter. Enforcement Rule art. 2 fixes the method only and leaves the decimal unaddressed — that one question does not close on the text.
To see all three taxes together, enter the floor area in the acquisition tax calculator. If the price is between 600m and 900m, read the marginal rate inside the slope alongside it.
