Korea's Newborn Special Mortgage: Rate Math and the 1.2% Floor

On a 30-year term, Korea's newborn special didimdol mortgage charges 2.05% for households with combined annual income under 20 million won and 4.50% for dual-income households in the 170–200 million won band. Borrow the same 400 million won and the monthly payment gap between those two brackets is 538,242 won. Those figures come from plugging the rate table published by the Housing and Urban Fund's MyHome portal into a standard amortization formula.

Rate discounts stack on top of that — subscription savings tenure, electronic contracts, additional births, minor children. However many you pile on, the final rate will not go below 1.2% per year. A separate floor caps the benefit.

Eligibility is narrow. You must have given birth to or adopted a child within two years of the application date (children born on or after January 1, 2023), be a household head who owns no home or one home, have combined annual income of 130 million won or less (200 million for dual-income couples), and hold net assets of 511 million won or less.

Rates by income bracket — 2.05% to 4.50% on a 30-year term

The MyHome rate table splits income into nine bands. Longer terms carry higher rates, so at a given income the spread between a 10-year and a 30-year loan runs about 0.25 to 0.30 percentage points.

Two adjustments sit on top. A home outside the capital region gets a 0.2 percentage point cut; a land-lease apartment adds 0.3 points. A household in the 60–85 million won band buying a provincial home on a 30-year term pays 2.70% instead of 2.90%.

The bracket boundaries deserve attention too. A line runs between 85 million and 100 million won, so the moment combined income moves from 85 million to 86 million, the 30-year rate jumps from 2.90% to 3.20% — 0.30 points. On a 400 million won loan, that one million won of income costs 64,947 won a month.

What 400 million over 30 years actually costs per month

A rate table alone does not convey the burden. The table below assumes equal principal-and-interest payments, a 30-year term, and a 400 million won loan, applying each bracket's rate. The formula is principal × monthly rate ÷ (1 − (1 + monthly rate)^-360).

Top to bottom, the five-year gap is 32.29 million won. Given that the special rate applies for a base period of five years, the income bracket effectively decides the cost of that entire window.

There is a catch in the table, though. Not every bracket can actually borrow 400 million won. The loan carries a DTI limit of 60%, meaning annual principal and interest cannot exceed 60% of annual income. At 20 million won of income, that allows 12 million won a year, or one million a month. Yet the first row's payment is 1,488,499 won — the full 400 million was never reachable. Working backward from the 60% DTI cap gives a maximum loan of roughly 268.73 million won.

Reverse the same math and, in the 20–40 million bracket at 2.40% over 30 years, reaching the full 400 million requires combined income of roughly 31.2 million won. Below that, the ceiling binds before the rate matters. Which regulation actually sets your limit is laid out in an earlier piece on which of LTV, DTI, and DSR decides the number.

The household sitting in the lowest cell of the rate table is not the one that can borrow the most — the cheapest rate and the largest loan sit at opposite ends.

How far down do the discounts actually take you?

The discount items published on the MyHome portal can be combined. Subscription savings held five years or more earn 0.3 points, ten years 0.4, fifteen years 0.5. An electronic real estate contract adds 0.1 (for applications through December 31, 2026), each additional birth 0.2, each minor child 0.1, and prepaying 40% or more of the balance 0.2.

Three realistic combinations, applied to the 60–85 million bracket on a 30-year term at 2.90%:

Shaving 0.8 points saves 166,359 won a month, or 9.98 million won over five years. That a single subscription savings account can swing 0.2 points on its own (five years versus fifteen) is a number worth having in hand before deciding whether to keep it open.

Then the floor kicks in. If the final rate after discounts falls below 1.2%, 1.2% applies. A household in the lowest income band on a 30-year term starts at 2.05%; take the 0.2 point provincial cut and the full 0.9 points of discounts and the arithmetic gives 0.95% — but the rate charged is 1.2%. In that band, adding more discount items buys nothing further.

After five years — additional births extend the window

The special rate runs for a base period of five years. Once it ends, a separate rate applies based on the combined income recorded when the loan was taken out. On a 30-year mortgage, only the first sixth of the term carries the guaranteed low rate.

The extension condition is childbirth. Each additional child born within two years of the application date extends the special rate period by five years, up to a maximum of fifteen. Two more children turn five years into fifteen. The 0.2 point additional-birth discount applies separately, so both the length and the level move together.

The rental side works differently. According to KB's guide, the newborn special beotimmok jeonse loan (lump-sum deposit lease financing) covers up to 80% of the deposit to a maximum of 240 million won, at a variable rate of 1.3–4.3%, with a base special period of four years. Its net asset limit is 345 million won, lower than the didimdol threshold. Comparing purchase financing and jeonse financing on the same terms will mislead you.

If prepayment is part of the plan, weigh two things together. Prepaying 40% or more earns a 0.2 point discount, but a prepayment penalty applies depending on timing. How that penalty decays with the remaining term is covered in a breakdown of mortgage prepayment penalties.

What to check

• Whether the birth date falls on or after January 1, 2023 — the birth or adoption must be within two years of the application date. A delayed application can erase eligibility.
• Where combined income sits relative to bracket edges — crossing 85 million, 100 million, or 130 million moves the 30-year rate in 0.30 point steps.
• Whether net assets stay within 511 million won — that is the didimdol threshold; beotimmok uses 345 million.
• The property's appraised value and floor area — above 900 million won in value or 85 square meters of exclusive area (100 in eup and myeon districts), the rate is irrelevant because you are not eligible.
• The amount your income clears under a 60% DTI — 400 million is a ceiling, not an entitlement. Check the reverse-calculated table first.
• Subscription savings tenure — 0.1 points changes at the five, ten, and fifteen year marks. Confirm which side of the line you are on before closing the account.
• Whether the property is outside the capital region — that earns 0.2 points. First-time buyers get 80% LTV, but capital-region and regulated-area properties revert to 70%.

Sources

• Newborn Special Didimdol Loan — Housing and Urban Fund MyHome Portal
• 2026 Newborn Special Loan: rates, limits, refinancing — KB