Income tax filing for employees with side income

Year-end settlement of salary does not always cover business, freelance or other side income. Determine whether a May comprehensive income tax return is needed.

Checked 2026-09-23 · Estimates and reference information, not legal or tax advice.

When salary settlement may be enough

A worker whose only relevant income is employment income fully settled by an employer may not need a separate comprehensive income tax return. Exceptions depend on the actual income and withholding history.

When a return may be needed

Business or freelance income, multiple employment incomes not combined at year-end, and certain other income can require a May return for the prior tax year. Keep payment and withholding statements.

The KRW 3 million other-income rule

A specified amount of other income after necessary expense deductions may be eligible for separate taxation. The KRW 3 million threshold applies to the legally defined other-income amount, not every gross side payment.

Missed deductions

The May return can also be a way to claim eligible deductions missed in an employer’s year-end settlement. Verify the filing period and supporting documents with the National Tax Service.

Sources

These Korean-language sources were checked on 2026-09-23. Laws and rates may have changed; consult the originals before an important decision.