Four ways not to waste time on tax — 5 years · 90% · 126 · 0.022% a day
If you overpaid, you can ask for it back within 5 years after the filing deadline. If you underpaid and fix it yourself before the tax office contacts you, the under-reporting penalty is cut by 90% within 1 month after the deadline and 75% within 3 months. If you are unsure, the National Tax Service line 126 charges no consultation fee. Late payment adds 0.022% a day with no reduction, so paying ₩10M 30 days late costs ₩66,000 more.
Conditions used in the calculation
- Overpaid
- request for correction, within 5 years after the statutory filing deadline
- Underpaid
- amended return, which reduces the under-reporting penalty (not if filed knowing the office would reassess)
- Reduction
- within 1 month after the deadline 90% · 3 months 75% · 6 months 50% · 1 year 30% · 1 year 6 months 20% · 2 years 10%
- Late-payment penalty
- 0.022% a day · no reduction
- Example
- ₩10M of tax paid 30 days late
- Basis
- 국세기본법 제45조의2 · 제47조의4 · 제48조 · 시행령 제27조의4
Results
- Claiming back overpaid tax
- within 5 years after the deadline
- Fixing it yourself
- 90% off within 1 month · 75% within 3 months
- ₩10M paid 30 days late
- ₩66,000 more
- Late-payment penalty
- 0.022% a day · not reduced
- NTS helpline
- 126 · no consultation fee (call charges apply)
At a glance
Counted from the statutory filing deadline. 국세기본법 제48조제2항제1호.
- 1 month90%
- 3 months75%
- 6 months50%
- 1 year30%
- 1.5 years20%
- 2 years10%
Why it works this way
Time wasted on tax is money wasted. Each deadline fixes how much you can claim back, how much of a penalty is forgiven, and how much is added every day.
국세기본법 제45조의2 and 제48조.
- Overpaidrequest for correction · within 5 years
- Underpaidamended return · 90% off within 1 month
- Within 3 months75% off · shrinking to nothing after 2 years
The reduction applies only to the under-reporting penalty. An amended return filed knowing the office would reassess gets no reduction.
If you are unsure, call the National Tax Service on 126. There is no consultation fee; you only pay the call charge.
Checked with the penalty-tax engine.
- Tax₩10M
- Per day0.022% = ₩2,200
- 30 days₩66,000 · no reduction
The late-payment penalty is not covered by the 제48조제2항 reduction.
The legal basis
Drawn from government announcements and the statutes themselves as primary sources, covering only the relevant part.
국세기본법 제45조의2 (request for correction)
In force Current (checked 2026-09-27, version effective 2026-08-11)
A taxpayer who filed by the deadline may request correction within 5 years after the statutory filing deadline when the tax reported exceeds the tax that should have been reported.
What this means
Overpaid tax does not come back on its own. After 5 years this route closes.
국세기본법 제48조제2항제1호 (penalty reduction)
In force Current (checked 2026-09-27)
Amended return within 1 month after the deadline: 90% of the under-reporting penalty; 3 months 75%; 6 months 50%; 1 year 30%; 1 year 6 months 20%; 2 years 10%. Not if filed knowing the office would reassess.
What this means
The sooner you fix a mistake, the less you pay. Waiting only lowers the reduction.
국세기본법 시행령 제27조의4 ① (late-payment rate)
In force Current (checked 2026-09-27)
22/100,000 per day.
What this means
0.022% a day looks small, but with no reduction it piles up day by day.
Run it on your own numbers
The calculator opens with these conditions already filled in. Change the figures and your own case comes straight out.
Open the Penalty Tax Calculator
Frequently asked
When do the 5 years start?
After that tax's statutory filing deadline. For global income tax that is May 31 (June 30 for returns needing a faithful-filing confirmation).
What if I fix it after the tax office contacts me?
An amended return filed knowing the office would reassess gets no reduction. You have to fix it yourself before they contact you.
Is the late-payment penalty reduced too?
No. The 제48조제2항제1호 reduction covers only the under-reporting penalty. 0.022% a day is added for every day you are late.
Is 126 free?
There is no consultation fee. The caller pays the call charge.
Results are estimates based on the inputs and on the rules as at the stated date. They may differ from a lender's actual assessment, and the rules change often. Take professional advice before any decision that matters.