Why a big year-end tax refund is not a win

“My colleague got ₩1 million back and I had to pay ₩300,000. What did I do wrong?” — probably nothing. The refund is not a score. It only tells you how much was withheld compared with what you really owed.

The settlement is a difference

Every month your employer withholds income tax using the official withholding table, which looks only at your pay and the number of family members. It is an estimate. In January the year is recalculated with your real deductions, giving your final tax (결정세액). Only the difference is settled:

Final tax (what you really owe for the year)
 − Tax withheld (what was taken from your pay)
──────────────────────────
 negative → refund / positive → you pay the rest

So a large refund mostly means too much was withheld during the year — you lent the government money without interest and got it back.

The number to compare is your final tax

If you and a colleague earn the same and your final tax is higher, that is where you are missing deductions. Every suggestion in the calculator is about lowering the final tax, not about growing the refund.

For foreign employees there is one more lever: the 19% flat rate. If it gives a lower final tax than the normal method, choosing it is a real saving. The calculator compares both.

You can choose how much is withheld — 80, 100 or 120%

You can ask your employer to withhold 80%, 100% (default) or 120% of the table amount.

• 80%: more take-home pay each month → more likely to owe at year-end
• 120%: less take-home pay each month → more likely to get a refund

Your final tax is exactly the same in all three cases. It is only a cash-flow choice. If you already ask your employer to withhold at the 19% flat rate, that replaces the table for you.

Common reasons you end up owing

1. Pay went up or a large bonus was paid — monthly withholding lagged behind your real income
2. A dependent dropped out — for example a child started working, but monthly withholding still assumed them
3. Few deductions and a high salary — the table assumes average deductions
4. You changed jobs — two employers’ income combined pushes you into a higher bracket

Owing is not a penalty; it is tax that was not withheld earlier. If the amount is over ₩100,000, you can ask your employer to split it over the February–April payslips.

Benefits that never show up as a refund

The child tax credit (partly) and the SME employee tax reduction are already reflected in monthly withholding, so you get them through higher take-home pay rather than a bigger refund. Cards, medical costs, rent and pension savings are not in the monthly table, which is why they drive the year-end refund.

Common questions

My final tax is already ₩0. Can I get more back? No. The most you can get back is what was withheld. Extra deductions do nothing once your final tax is ₩0.

What if I skip the settlement? Your employer settles with only the basic deduction for you, so you lose card, medical, pension and other deductions. Missed items can still be claimed in the May income tax return or by a claim for correction within five years.