What Income Must Be Reported to Both Countries?
미국과 한국 양쪽에 보고해야 하는 소득 — 완전 매트릭스 2026
Bidirectional reporting obligations for U.S. and Korean tax residents, including how 국민연금 (National Pension) benefits are taxed by Korea and what that means for the FTC analysis.
Overview — Reporting ≠ Taxation 신고 의무 ≠ 과세 — 핵심 구분
A U.S. tax resident reports all worldwide income to the U.S.; a Korean tax resident reports all worldwide income to Korea. Many Korean nationals and Korean-Americans are dual residents under domestic law in both countries (even when a treaty tie-breaker assigns primary residency to one side for treaty purposes), meaning the same income may need to be disclosed to both tax authorities — even when only one country ultimately taxes it.
Bidirectional Obligations — Both Directions 양방향 신고 의무
This guide's distinguishing feature is recognizing that the reporting obligation runs in both directions — a fact often overlooked in U.S.-centric guidance.
- Report ALL worldwide income to the U.S. on Form 1040
- Includes Korean salary, rental, business, investment, severance, and pension income
- Even if Korea already taxed it
- FBAR and FATCA for Korean accounts/assets above thresholds
- Report ALL worldwide income to Korea on 종합소득세 신고 (by May 31)
- Includes U.S. salary, rental, business, investment, and other income
- Even if the U.S. already taxed it
- 해외금융계좌 신고 for U.S. accounts/assets above 5천만원 (~$37,000)
Master Matrix 전체 매트릭스
| Income Type | Report to U.S.? | Report to Korea? | Primary Taxing Right | FTC Available? |
|---|---|---|---|---|
| Korean salary 근로소득 | YES | YES | Korea | YES |
| Korean rental income 임대소득 | YES | YES | Korea | YES |
| Korean business income 사업소득 | YES | YES | Korea (if PE) | YES |
| Korean listed stock gains (individual) | YES | USUALLY NO | U.S. | NO |
| Korean ETF/mutual fund gains (PFIC) | YES (Form 8621) | YES | Mixed | PARTIAL |
| Korean interest 이자소득 | YES | YES | Korea | YES |
| Korean dividends 배당소득 | YES | YES | Korea | YES |
| Korean severance 퇴직금 | YES (if post-residency) | YES | Korea | YES |
| Korean private pension (연금저축, IRP distributions) | YES | YES | Mixed | YES |
| 국민연금 (National Pension) benefits | YES (Social Security-like) | YES — see below | Both — Korea taxes as 연금소득; treaty Social Security provisions may apply | POSSIBLY — requires analysis |
Income Categories — Detailed 소득 유형별 상세 설명
Report on Form 1040 Line 1a. Worldwide income — fully reportable regardless of where earned.
If Korean tax resident: report on 종합소득세 (or via 연말정산 if sole income is from one Korean employer).
Schedule E. U.S. depreciation rules apply (27.5/39 years), independent of Korean depreciation treatment.
Korean real property income is always Korean-source — reportable to Korea regardless of the owner's residency.
Schedule C. Subject to U.S. SE tax unless the Totalization Agreement exception applies (국민연금 contributor with Certificate of Coverage).
Korean business operations generate Korean-source income reportable to Korea via 종합소득세, regardless of the owner's other residency.
Schedule D / Form 8949. Fully taxable at U.S. LTCG/STCG rates.
Korea exempts small shareholders (소액주주) from capital gains tax on KRX-listed stock — most individual investors owe no Korean tax on these gains.
Taxable ONLY if received after the U.S. residency start date. Payment date controls, not the period of service.
Korea taxes 퇴직금 as 퇴직소득 (severance income) using a special calculation formula regardless of the recipient's later residency status — the tax is withheld by the Korean employer at payment.
국민연금 — How It's Actually Taxed 국민연금 과세 방식
국민연금 (National Pension) old-age pension (노령연금) benefits are taxed as 연금소득 (pension income) when received — to the extent the benefits are attributable to contributions made after January 1, 2002. This is because contributors received an income tax deduction (소득공제) for their own contributions starting in 2002 — in exchange for that upfront tax benefit, the eventual pension payout is taxed. This is the standard "EET" (Exempt-Exempt-Taxed) structure used in many countries' pension systems, including the U.S. 401(k) and traditional IRA.
Key Mechanics
- Pre-2002 contributions are NOT taxed upon distribution — because no deduction was given when those contributions were made (pre-EET system). For long-time 국민연금 participants, the pension administrator (국민연금공단) calculates the taxable vs. non-taxable portion of each payment based on contribution history.
- 국민연금 is subject to mandatory comprehensive taxation (종합과세) — unlike private pension products (연금저축, IRP), which can elect a 15% separate taxation rate when total private pension income exceeds KRW 15,000,000/year, 국민연금 benefits must always be combined with other income and taxed at the progressive 종합소득세 rates (6.6%–49.5%).
- Monthly withholding + January year-end settlement: 국민연금공단 withholds tax monthly using a simplified tax table, then performs a 연말정산 (year-end settlement) when paying the January benefit. If the recipient has no other income besides the public pension, this 연말정산 typically completes their tax obligation with no separate 종합소득세 filing required.
- Comprehensive filing required if combined with other income: If the recipient has other income — financial income exceeding KRW 20,000,000, business or wage income, or other income exceeding KRW 3,000,000 — the 국민연금 benefit must be combined with that other income and reported via the May 종합소득세 filing.
U.S. Side — What This Means for FTC
4 Fully Computed Examples 실제 계산 사례 4개
Common Mistakes 자주 발생하는 오류
- 1 Assuming 국민연금 benefits are entirely tax-free in Korea. Post-2002 contributions generate taxable pension income (연금소득) upon distribution under Korean Income Tax Act §20-3/§22. Only pre-2002 contributions remain untaxed at distribution. For most current and future retirees, a meaningful portion of their 국민연금 benefit is Korean-taxable.
- 2 Concluding "no FTC available" for 국민연금 simply because it's a government pension. The FTC availability depends on whether Korean tax was actually paid on the benefit — which, per the corrected analysis above, it often is for post-2002 contributions. Defaulting to "no FTC" without checking the actual Korean tax withholding overlooks real credit opportunities.
- 3 Assuming only one country's reporting obligation applies when dual residency exists. A person who meets the domestic residency test of both the U.S. and Korea simultaneously must report worldwide income to BOTH countries — the treaty tie-breaker resolves which country has primary taxing rights, not which country gets reporting from the taxpayer.
- 4 Confusing reporting obligation with tax liability."I don't owe tax to Korea on this" does not mean "I don't need to report this to Korea" if Korean domestic residency applies — and vice versa for the U.S. Reporting and taxation are governed by different rules.
- 5 Not distinguishing 국민연금 from private pensions (연금저축, IRP) for Korean tax purposes. 국민연금 is subject to mandatory comprehensive taxation (종합과세) with no separate-taxation election. Private pensions can elect 15% separate taxation when annual benefits exceed KRW 15,000,000. Treating them identically misstates the Korean tax computation.
- 6 Assuming Korean listed stock gains always escape Korean tax. The 소액주주 (small shareholder) exemption applies to most individual retail investors — but large shareholders (대주주, generally those holding above specified ownership/value thresholds) ARE subject to Korean capital gains tax on listed stock sales. Verify shareholder classification before assuming the exemption applies.
- 7 Not reporting U.S. income to Korea when Korean domestic residency applies. The bidirectional nature of this analysis means Korean tax residents (determined by Korea's own 183-day or domicile tests) must report U.S.-source income to Korea — a direction frequently overlooked when most cross-border guidance focuses only on the U.S. reporting side.
- 8 Not verifying the pre-2002/post-2002 contribution split for 국민연금 recipients. 국민연금공단 calculates and discloses this split on official pension statements — the taxpayer should request this breakdown rather than assuming either full taxation or full exemption.
Hanmi CPA Insight
The bidirectional nature of cross-border reporting is the conceptual foundation that most U.S.-focused guidance omits entirely. It is intuitive to think of "Korean income reported to the U.S." as the whole story — but a meaningful number of Korean nationals and Korean-Americans are simultaneously Korean tax residents under Korean domestic law, with their own independent obligation to report U.S.-source income to the Korean NTS. The treaty tie-breaker resolves which country has primary taxing rights; it does not excuse either country's citizens or residents from that country's own reporting requirements during the period of dual residency.
The 국민연금 taxation rule matters because it changes a planning conclusion, not just a technical detail. A CPA or taxpayer who assumes Korea doesn't tax 국민연금 will not look for Korean tax documentation, will not check Form 1116 eligibility, and may end up paying full U.S. tax on a pension benefit where Korean tax was, in fact, withheld and creditable. The accurate starting position — Korea taxes post-2002 contribution-derived 국민연금 benefits as ordinary pension income, subject to mandatory comprehensive taxation — opens the door to FTC analysis. For the growing population of Korean-American retirees who spent meaningful careers contributing to 국민연금 before relocating to the U.S. (or vice versa), this is not a minor footnote — it can be the difference between a properly computed return and an overstated U.S. tax bill.
The general principle that should replace any blanket assumption about Korean taxation: verify the actual Korean tax treatment for each income category, in each specific year, before concluding whether FTC is available. Korean tax law changes (such as the EET restructuring of pension taxation in 2002, the introduction of separate taxation elections for private pensions, and ongoing reforms to capital gains exemptions) mean that static assumptions about "what Korea taxes" age poorly. A CPA-driven, category-by-category verification — rather than reliance on generalized rules of thumb — is what actually protects against both double taxation and overpayment.