AI Korean Income Tax Filing — 30 Minutes (Korean Residents 2026)
Filing Korean Comprehensive Income Tax (종합소득세, "jongsose") takes the average self-employed person 5 hours. With 6 million self-employed Koreans filing in May, that's 30 million hours of national tax-filing time annually.
Tax N Benefit (세금N혜택) cut that to 30 minutes using Claude AI + Korea National Tax Service (NTS) API integration. This guide walks through it step-by-step.
Who needs to file 종합소득세?
You need to file Korean Comprehensive Income Tax if:
- You're a Korean tax resident (183+ days in Korea OR domicile here), AND
- You have income other than salary alone (freelance, business, rental, multi-source).
Salary-only employees: handled through 연말정산 (year-end settlement) in February — no May filing needed.
Everyone else: May 31 deadline. Miss it = 20% non-filing penalty + late payment interest.
Before vs After — Filing Time Comparison
| Step | Direct (Hometax) | Tax Accountant | AI Service |
|---|---|---|---|
| Document gathering | 2–3 hours | 1 hour (handover) | 5 min |
| Item entry | 1–2 hours | 0 | 0 |
| Missing-item check | 0.5–1 hour | 0 | 0 |
| Review | self | 1–3 days wait | 5 min |
| Submission | 30 min | 0 | 5 min |
| Cost | ₩0 | ₩300K–800K | 9.9% post-pay |
| Total | 5+ hours | 1–3 days | ~30 min |
Why AI filing is fast
1. Direct NTS API integration
After login, one-time consent lets us pull income data, payment statements, and year-end settlement records directly from Hometax. No paper, no screenshots, no manual typing.
2. AI auto-detects missed deductions
- Yellow Umbrella deduction (노란우산공제, up to ₩5M deduction)
- Pension savings + IRP (up to ₩9M tax credit)
- Credit card business-use allocation
- Asset depreciation balance
3. Natural-language input
"I bought a ₩2M camera last year — how do I handle this?"
→ AI explains + auto-registers it under depreciation.
4. Optional CPA review
If you want extra assurance, +₩50K adds CPA review (simple cases only).
30-Minute Filing — Step-by-Step
- Visit tax-n-benefit-api.vercel.app
- Login via Kakao or Naver (1 second)
- Enter business registration number
- (Optional) Upload card statement PDFs, tax invoices
- Authenticate with Hometax (joint certificate or Kakao)
- One-time user consent → automatic data import
- Income, payment statements, year-end records auto-populated
- "Are you enrolled in the Yellow Umbrella deduction?"
- "Do you rent? Is the property's standard value under ₩400M?"
- "Do you have a vehicle/laptop used for business?"
- Each answer updates your refund estimate in real time.
- Refund / tax owed / potentially missed items
- (Optional) +₩50K CPA review
- Confirm submission
- One-click submission to Hometax
- 9.9% auto-deducted after refund deposits (no upfront payment)
- Refund 0 → fee 0 (under refund-protection policy)
Recommended for
Recommended:
- Self-employed / freelancers (single income source)
- Multi-jobbers (≤3 income sources)
- Delivery riders
- YouTubers / creators
Not recommended (use a CPA):
- Multiple corporate ownership
- Mixed foreign income + Korean income + real estate sales
- Currency conversion cases
- Prior tax-audit history
Trust signals
- Business registration: 552-59-00848 (registered Korean business, software development, opened 2026-04-01)
- PG: BillGate (registered Korean payment gateway, PCI-DSS certified)
- AI engine: Claude API (Anthropic official)
- NTS API: Official integration
- Privacy: Documents discarded immediately after filing (0-day retention)
One important caveat
AI is a tool, not a CPA.
- Simple cases: AI alone is sufficient (~98%)
- Complex cases: AI + CPA review recommended
- Very complex: see a CPA from the start
Filing deadline May 31 · D-26
From 5 hours to 30 minutes
9.9% post-pay · Refund 0 → fee 0 (under refund-protection policy)
FAQ
Q. Can foreign residents in Korea use this?
A. Yes, if you're a Korean tax resident. The interface is currently Korean-first; English UI is on the roadmap. For foreign-engineer 5-year reduction or treaty benefits, we recommend an English-speaking CPA.
Q. Who's responsible if AI makes a mistake?
A. Filings reviewed by AI + optional CPA review fall under our penalty-coverage policy. Excludes cases where the user submitted incomplete or incorrect documents.
Q. Data security?
A. Official NTS API (MyData format) + immediate document deletion + end-to-end HTTPS. BillGate PG is PCI-DSS certified.
Q. What if my refund deposit is delayed?
A. NTS refunds within ~30 days of filing. Our 9.9% fee is charged only after refund deposits — never upfront.