Global Income Tax Return (종합소득세)
종합소득세 is Korea's annual return for income that was not fully settled elsewhere. It is filed in May for the previous calendar year, and its defining feature is in the name: separate income streams are combined into one figure and taxed together at progressive rates. That combination is why a second income source can push the tax on your first one higher than people expect.
Who this affects
- Freelancers and independent contractors (3.3% withholding is a prepayment, not a settlement)
- Sole proprietors and business owners
- Employees with meaningful additional income — rental, business, or financial
- Anyone with multiple employers during the year whose income was not consolidated
3.3% withholding is a deposit, not a final tax
Freelancers routinely assume the 3.3% deducted at source closes the matter. It does not — it is a prepayment credited against the tax computed in May. Depending on your income and expenses, the May return can produce a refund or a further bill.
Recognised expenses decide the outcome
Business and freelance income is taxed on profit, not turnover, so what you can substantiate as an expense drives the result. Korea also allows standard-rate estimation methods for smaller operations that have not kept full books — which method applies depends on your revenue scale and bookkeeping.
Filing and paying are one deadline here
Unlike the US, the May deadline covers both the return and the payment. Instalment arrangements exist for larger liabilities, but they have to be requested — they are not automatic.
Not everything is combined
Certain income is taxed separately rather than being rolled into the global figure — severance and some financial income among them. Treating separately-taxed income as global income (or the reverse) is one of the more expensive filing errors.
Common questions
I'm an employee. Do I need to file in May?
Usually not, if salary from one employer is your only income and 연말정산 settled it. You do need to file if you had additional income of a reportable size, or worked for multiple employers without consolidating.
I earned very little as a freelancer. Should I still file?
Often it is worth it. If the 3.3% withheld exceeds the tax actually due once expenses and deductions are applied, filing is how you get the difference back. Skipping it usually means leaving your own money with the tax office.
What happens if I miss the May deadline?
Penalties apply for late filing and late payment, and they accrue separately. Filing late is still materially better than not filing — the penalty structure treats non-filing more harshly.
Official sources
General information, not tax advice. Rules and thresholds change, and how they apply depends on your circumstances — confirm with a licensed professional before acting.