Side Income in Korea: Must You File in May? The Provision Lists Only Who Need Not

Earn a few million won on the side in Korea and the same question follows: “do I have to file in May?” The internet answer is a slogan — “business income always, other income above 3 million” — so we opened the provision it rests on.

It is Income Tax Act art. 73 (exceptions to the final return). And the provision does not define who must file. It lists, in nine subparagraphs, only those who need not. Fall outside the list and you file.

Your income mix, run through the provision

Paragraph (2) is the one people miss. “Paragraph (1) shall not apply to a person having any of the following income received from two or more persons (excluding daily workers)” — employment income included. A second job that pays wages triggers a filing duty too.

It carries a proviso, though: “provided that this shall not apply to a person who, through the year-end settlement … and payment of income tax …, has no tax payable on the final return.” Settle both salaries at year-end with nothing left owing and the exemption survives.

“Employment plus business income” is simply not in the list. Paragraph (1) enumerates combinations ending in “only” — only employment, only retirement, only public pension — and a few pairs of those. The moment 3.3%-withheld side income sits alongside a salary, you are outside it.

“Separate taxation” is what the exemption hangs on

Subparagraph 9 forgives separately taxed interest, dividend, pension and other income. What counts as separately taxed is set — in won — by art. 14(3).

Only the other-income test uses a net figure. Interest, dividends and rent are measured on the combined amount or gross receipts — money received. Other income is measured after necessary expenses, so for personal services (60% deemed expense) 7.5 million won of fees equals 3 million won of other income (our arithmetic: 7.5M x 40% = 3M).

And subparagraph 8(a) ends with a proviso beginning “provided that, where a resident with such income …” — separate taxation is elective. Someone in a low bracket may prefer to combine.

The 3.3% is a separate matter from filing

Withholding applies a flat percentage to the gross payment. Art. 129(1)3 sets “3/100 on business income subject to withholding”, and Local Tax Act art. 103-13(1) adds “10/100 of the income tax withheld”, giving 3.3% (our arithmetic).

That percentage sees none of your expenses, dependants or salary. So filing produces refunds in some cases and extra tax in others. The full breakdown is in where the freelance 3.3% actually comes from.

How far apart the two figures sit depends on the rate table, which the previous edition could not print: the table in Income Tax Act art. 55(1) is served as an image by the Korean Law Information Center. This time we found the table written out in the image's alt text, and copied it from there.

^* This one figure is ours, not the statute's. The alt text's last row carries no fixed amount — only “45 per cent of the amount exceeding 1 billion won.” The seven rows above it all chain exactly as previous fixed amount + band width × previous rate (0.84 → 6.24 → 15.36 → 37.06 → 94.06 → 174.06m), and one more step of the same rule gives 384.06m won. The asterisk marks it as a figure we computed rather than read.

Set that table beside the 3.3% and the withholding stops looking like a tax and starts looking like a deposit.

Non-filing penalty — Framework Act on National Taxes art. 47-2

Paragraph 1 sets the penalty as the unfiled tax payable multiplied by the following rates.

The widely repeated “20%, or 40% if fraudulent” was right. What it omitted is the 60% for offshore fraud, and a second layer: paragraph 2 subparagraph 1 requires double-entry bookkeepers and corporations to also compute gross receipts × 14/10,000 (fraud) or 7/10,000 (otherwise) and pay whichever is larger. Small tax but large receipts, and the receipts side wins.

Most people starting a side job are simplified-bookkeeping taxpayers and so fall outside paragraph 2 subparagraph 1. The threshold is in Enforcement Decree art. 208(5): you are a simplified-bookkeeping taxpayer if you started the business this year, or if last year’s receipts were below KRW 300 million (farming, fishing, wholesale and retail, etc.), 150 million (manufacturing, lodging and food, information and communications, etc.) or 75 million (professional, scientific and technical services, education, arts and sports, personal services, etc.). Licensed professionals such as doctors and lawyers (art. 147-2) are excluded regardless of amount. Which row you fall in follows the trade code on your business registration.

When the deadline is a Sunday — Framework Act on National Taxes art. 5(1)

Where a filing or payment deadline falls on (i) a Saturday or Sunday, (ii) a public holiday or substitute holiday under the Public Holidays Act, or (iii) Labour Day, the provision makes “the following day the deadline.” Subparagraph 3 (Labour Day) was added on 11 November 2025.

31 May 2026 is a Sunday. The deadline for that year is therefore Monday 1 June — the sentence the previous edition removed for want of a source, restored here with the provision attached.

When, where, and what gets combined

• Window — art. 70(1): “from 1 May to 31 May of the year following the taxable period, to the head of the competent tax office.”
• Taxable period — art. 5: 1 January to 31 December.
• Place of tax payment — art. 6(1): “the place of tax payment for a resident's income tax shall be the place of domicile” (residence if none). Not the employer's address.
• What combines — art. 4(1): global income is interest, dividend, business, employment, pension and other income. Retirement income and capital gains are excluded.
• How — verbatim: “electronic filing via Hometax, electronic filing via mobile Sontax, or filing through a tax agent …”

Liability by bracket is in the comprehensive income tax article, your own figures in the calculator, and missed years in the amended return.

Widely repeated, and unsourced

These sentences were in the previous edition and are not supported by anything we opened. Plausible-sounding claims are the dangerous kind, so they are listed rather than quietly dropped. Three of them we have now filled in from the statutes — the “filled” rows below.

Simple-books and double-entry lines, with a checker, are in simple books or double-entry.

Questions that remain

My side income is small — does that exempt me?

Art. 73 contains no monetary test. The exceptions are defined purely by the combination of income types.

That said, business income does not automatically put you outside the list. Subparagraph 4 of paragraph 1 exempts a person with only “business income subject to withholding under art. 127 and prescribed by Presidential Decree”, and that Decree is Enforcement Decree art. 137(1). Opening it, the list is three trades.

• Insurance solicitors — “a person who, in an independent capacity, solicits policyholders and receives commission according to results”
• Door-to-door and sponsored door-to-door salespeople under the Door-to-Door Sales Act
• Contract beverage delivery sellers — “delivering beverages without opening a place of business”

All three must also be simplified-bookkeeping taxpayers (art. 160(3)), and for the second and third the exemption applies only where the withholding agent has carried out the year-end settlement (proviso to the same paragraph). Blogging, YouTube, delivery riding and lecture fees are nowhere in those three lines — so they are outside the list, whatever the amount.

Will my employer be told?

On the income-tax side there is still no notification rule — the provisions establish only that tax is filed at your place of domicile (art. 6(1)). But what people actually worry about is the health insurance premium, so on 18 September 2026 we opened that instead.

The short answer: the premium on non-wage income is paid by you, not your employer.

Paragraph (3) requires the employer to deduct and remit only the wage-based premium, and to tell the employee the amount deducted. The non-wage share is not in that sentence — it never passes through payroll and is billed to you directly.

The threshold and the timing are in the text too.

Paragraph (3) is what you feel. Premiums charged from January to October run on income from two years earlier — the bill for a side income arrives close to two years later. “Nothing happened” may simply mean it has not arrived yet.

We still will not write “your employer can never know”. What the provisions settle is who pays. What the insurance service notifies a workplace about is practice outside the text — ask the National Health Insurance Service (1577-1000).

Is blog or video income business income?

The test is character, not amount: “income from activity carried on continuously and repeatedly on one's own account and responsibility for profit” (art. 19). Which side a particular case falls on depends on the substance, so we do not decide it here.

Do Korean stock gains combine?

Art. 4(1) excludes capital gains from global income. Which shares are taxable on disposal is in art. 94(1)3 of the same Act (checked 23 September 2026): listed shares sold by a major shareholder, or sold off-exchange by anyone, plus unlisted shares (except SME and mid-sized-company shares a minority holder sells on the KOFIA over-the-counter market) and foreign shares. Listed Korean shares a minority holder sells on the exchange are not on the list. The major-shareholder thresholds are in Enforcement Decree art. 157 (checked 8 October 2026): a holding of 1% or more of the company (2% on KOSDAQ, 4% on KONEX) or shares in it worth 5 billion won or more, measured at the end of the previous business year. For the largest-shareholder group the holdings of relatives and other related parties are added together, and buying up to the percentage threshold during the year makes you a major shareholder from that purchase date (para. 9). Interest and dividends above 20 million won combined do come into global taxation (art. 14(3)6).

What about severance pay?

No. Art. 4(1) separates retirement income from global income.

The same provision (Article 73) is read again from an ordinary employee’s side in who need not file a final return, and how much tax comes off other income such as lecture and manuscript fees — 60% deemed expenses, 20% withholding, nothing at 50,000 won or less per case — is worked out in tax on lecture and manuscript fees.

When a side job becomes a business there is one more deadline at the tax office — registration within 20 days of starting, or 1% of sales if late (business registration deadline).

Sources

• Korean Law Information Center — statute — Income Tax Act Enforcement Decree art. 208(5) (simplified-bookkeeping thresholds) and Framework Act on National Taxes art. 47-4 with Decree art. 27-4 (late-payment rates).
• Korean Law Information Center — statute — Income Tax Act art. 73 (exceptions to the final return) (in force 1 Jan 2026, Act no. 21221). Source for the nine exemption subparagraphs, the “two or more payers” exclusion in paragraph (2), and its proviso.
• Korean Law Information Center — statute — Income Tax Act art. 14 (computation of the tax base). Source for the 3M / 20M / 20M won thresholds and the proviso making separate taxation elective.
• Korean Law Information Center — statute — Income Tax Act art. 129 (withholding tax rates). Source for 3/100 on business income.
• Korean Law Information Center — statute — Local Tax Act art. 103-13 (duty of special collection). Source for “10/100 of the income tax withheld”.
• Ministry of Government Legislation, Easy-to-Find Practical Laws — “Comprehensive real estate holding tax and comprehensive income tax” (page states as of 15 June 2026). Source for the six categories of global income (art. 4(1)), the taxable period (art. 5) and the place of tax payment (art. 6).
• Ministry of Government Legislation, Easy-to-Find Practical Laws — “Delivery app workers > Filing the comprehensive income tax return” (page states as of 15 July 2026). Source for the definition of business income, the May window, the consequence of not filing and the filing methods.
• Korean Law Information Center — statute — Income Tax Act art. 55 (tax rates), as amended 31 Dec. 2022. Source for the eight rows of the global income rate table. The table is served as an image; the text lives in the image's alt attribute — and the last row's fixed amount is missing there, so we computed it.
• Korean Law Information Center — statute — Framework Act on National Taxes art. 47-2 (non-filing penalty). Source for 20/100, 40/100, the 60/100 offshore case, and the gross-receipts comparison in para. 2 subpara. 1.
• Korean Law Information Center — statute — Framework Act on National Taxes art. 5 (special cases for deadlines), as amended 11 Nov. 2025. Source for “the following day” on weekends, public and substitute holidays and Labour Day.
• Korean Law Information Center — statute — Income Tax Act Enforcement Decree art. 137. Source for the three trades behind art. 73(1)4 and the simplified-bookkeeping and year-end-settlement conditions.
• Our own arithmetic — 3% x 1.1 = 3.3%, 7.5M won of fees = 3M won of other income, the 6.6 / 16.5 / 26.4 / 38.5 / 41.8% figures (rate × 1.1), the 384.06m won in the last row of the rate table, and the required / exempt verdicts — all our matching or chaining of the provisions.

Where to check further

• Whether your platform earnings are business income or other income. The “continuous and repeated” test turns on substance, so this article does not rule case by case. The answer changes both your rate and how you file — put your own transaction records to the NTS helpline (126) or your district tax office.
• The late-payment penalty — opened on 22 September. Filing on time but paying late falls under art. 47-4: 0.022% a day from the day after the deadline (about 8.03% a year; Decree art. 27-4(1)), a one-off 3% if a notice is issued and still not paid by its deadline, and 0.67% a month after that (added February 2026). A worked example is in the gift tax penalty article.
• Whether you are a simplified-bookkeeping taxpayer — opened on 22 September. The three thresholds from Decree art. 208(5) are in the note above; what remains is which trade row applies to you.
• The last row of the rate table. The 384.06m won fixed amount above 1 billion won is our own chaining — the alt text did not carry that number. Hometax rate guidance can be used to check it.

Art. 73 does not list who must file — it lists who need not. If your combination is not on that list, the default applies.

As of July 2026 (Income Tax Act and Local Tax Act in force 1 Jan 2026; guidance pages as of 15 Jun and 15 Jul 2026). Provisions and amounts are the Korean Law Information Center and the legal guidance service verbatim; the per-combination verdicts and the multiplications are ours. This is not tax advice — how a particular income is classified depends on substance, so confirm through Hometax or a tax professional.