Jaehun (not his real name) was watching the news last month when he heard the anchor say: “May is the month for comprehensive income tax filing.” He muttered to himself, “I’m a salaried employee. My company handles all that through year-end settlement. That has nothing to do with me.” He changed the channel.
A few days later, over lunch, his friend Seungmin said casually:
“Hey, didn’t you open a Smartstore last year? If you made any income there, you need to file a comprehensive income tax return, you know?”
Jaehun set down his chopsticks. He hadn’t made a lot from the Smartstore — maybe a few hundred thousand won — but it was income. It had never once occurred to him that he needed to file.
“Wait… am I actually required to file?”
Cold sweat. The deadline was May 31st, he was told. And there would be penalties for missing it. This guide is for everyone who, like Jaehun, assumed “I’m a salaried worker, so it doesn’t apply to me” — and is now wondering if they need to act before the end of May.
What Is Comprehensive Income Tax? One Sentence
Comprehensive income tax (종합소득세) is the annual tax filing where all types of income are combined and reported to the tax authority. For salaried employees with only wage income, year-end settlement (연말정산) handled by their employer is sufficient. But if you have any income beyond your salary, you must file your own return in May.
- Salary only → Year-end settlement covers it; no additional filing needed
- Salary + other income → Must file comprehensive income tax in May
| Income Type | Examples |
|---|---|
| Business income | Freelance work, Smartstore, YouTube/blog revenue, tutoring |
| Rental income | Monthly rent received from property |
| Financial income | Interest + dividends combined over ₩20 million/year |
| Miscellaneous income | Manuscript fees, lecture fees, prizes, lottery winnings |
| Multiple wage income | Salary from two or more employers in the same year |
Does This Apply to Me? 5-Point Checklist for Salaried Workers
① You have side income or freelance earnings
Smartstore, Coupang Partners, YouTube revenue, blog ad income, Kmong/Taling gigs, freelance translation or design — regardless of the amount, any business income outside your salary makes you a filing candidate. “It was only a few hundred thousand won” is not a safe assumption. Income is income, and it must be reported in principle.
② You receive rental income
If you own property and collect rent, you may need to file. For housing rental income, filing is mandatory when annual rental income exceeds ₩20 million. Even below that threshold, you may elect a separate taxation option. Anyone collecting rent — even from a single property — should check their situation.
③ Your financial income exceeded ₩20 million
If the combined total of interest and dividends you received exceeds ₩20 million in a year, you fall under comprehensive financial income taxation. With recent high interest rates, more people have been crossing this threshold through savings and bonds.
④ You received wages from two or more employers
If you changed jobs or worked two jobs during the year, income from all employers must be combined. Year-end settlement is typically processed only at your primary employer, leaving the other income potentially under-taxed. Job-changers, take note.
⑤ Your year-end settlement was incomplete or had missed deductions
If you missed deduction items during year-end settlement, or if your income changed in ways that weren’t reflected, the May filing period is your opportunity to correct the record — which may result in a refund or additional payment.
How and When to File — Simpler Than You Think
Filing period
The filing and payment period is May 1–31 every year. The deadline for most salaried workers with side income is May 31st.
Filing via Hometax (PC)
- Go to the National Tax Service Hometax website (hometax.go.kr)
- Log in with your certificate or simple authentication (Kakao, Naver, etc.)
- Navigate to Tax Filing → Comprehensive Income Tax
- Select the appropriate return type and review your income
- Confirm or correct information, then submit
First time? Use the Pre-Filled Return (모두채움 신고)
The NTS Pre-Filled Return feature auto-populates income and deduction fields based on data the tax authority already has. For first-time filers or those with simple income structures, this dramatically simplifies the process. Review what’s been filled in, make corrections if needed, and submit.
Mobile filing: Sontax app
The Sontax app (손택스) on iOS and Android offers the same functionality as Hometax on mobile. Simple authentication login makes it accessible without certificates. Many people find it faster than using a desktop browser.
What Happens If You Don’t File?
| Penalty Type | Rate | Condition |
|---|---|---|
| Non-filing penalty | 20% of tax due | Missed the filing deadline |
| Fraudulent non-filing penalty | 40% of tax due | False or concealed information |
| Late payment penalty | 0.022% per day | Accrues daily on unpaid amount |
If your tax due is ₩500,000, the 20% non-filing penalty alone adds ₩100,000. Late payment penalties accumulate daily on top of that. The penalties can easily exceed what you’d have paid on time.
Just 10 Minutes Before May Ends
Comprehensive income tax sounds intimidating. It’s actually much simpler than the name suggests. Start by logging into Hometax and checking whether any income appears under your name. Open the Pre-Filled Return screen and you’ll see what the NTS already knows about your income. That one screen tells you whether you need to file.
Invest 10 minutes before May 31st. It’s far better than paying unnecessary penalties later.
⚠️ Disclaimer: This article is for general informational purposes only. Tax obligations vary significantly by individual income type, amount, and deduction circumstances. For accurate guidance, please check your details on Hometax directly or consult a licensed tax accountant or the NTS helpline (126).