JP Social Insurance

Section 1 -- Quick reference

Quick reference table

Field	Value
Country	Japan
Jurisdiction Code	JP
Primary Legislation	National Health Insurance Act; National Pension Act
Supporting Legislation	Long-Term Care Insurance Act; Local Tax Act
Tax Authority	Municipal governments (NHI); Japan Pension Service (National Pension)
Tax Year	FY 2025 (April 2025 -- March 2026)
Currency	JPY only
Contributor	Open Accountants Community
Validated By	Pending -- requires sign-off by a Japanese tax accountant or social insurance labour consultant
Validation Date	Pending
Skill Version	2.0
Confidence Coverage	Tier 1: National Pension fixed amount, NHI component structure, payment schedules, caps. Tier 2: NHI municipal rate variations, reduction eligibility, partial-year calculations. Tier 3: disability pension, survivors pension, voluntary additional pension.

National Pension (FY 2025)

Item	Amount
Monthly premium	JPY 17,510
Annual total	JPY 210,120
Category 1 insured	Self-employed, freelancers, students, unemployed aged 20-59
Tax treatment	Fully deductible as social insurance premium deduction

NHI component structure

Component	Purpose	Applies To
Medical	Basic health insurance	All NHI enrollees
Support	Elderly health system support	All NHI enrollees
Long-term care	Long-term care insurance	Ages 40-64 only

NHI annual caps (FY 2025)

Component	Annual Cap
Medical	JPY 650,000
Support	JPY 240,000
Long-term care	JPY 170,000
Total maximum	JPY 1,060,000

NHI sub-elements per component

Sub-Element	Basis	Typical Range
Income-based	Prior-year income minus JPY 430,000 base deduction	5-12% (varies by municipality)
Per-capita	Fixed amount per enrolled person	JPY 20,000-60,000/year
Per-household	Fixed amount per household	JPY 0-30,000/year (some omit)
Asset-based	Fixed-asset tax	Being phased out

Low-income reductions (NHI per-capita/per-household only)

Reduction	Household Income Threshold (2025)
70% reduction	JPY 430,000 + (JPY 100,000 x earners beyond 1)
50% reduction	JPY 430,000 + JPY 295,000 x insured + (JPY 100,000 x earners beyond 1)
20% reduction	JPY 430,000 + JPY 545,000 x insured + (JPY 100,000 x earners beyond 1)

Conservative defaults

Ambiguity	Default
Unknown municipality	Flag for reviewer -- cannot compute NHI without municipal rates
Unknown prior-year income	Use JPY 0 (minimum NHI, possible pension exemption)
Unknown age	Assume under 40 (no long-term care component)
Unknown shakai hoken status	Assume NOT enrolled (NHI applies)

Read this whole section before computing anything.

Section 2 -- Required inputs and refusal catalogue

Required inputs

• Required inputs before computing — Before computing any social insurance figure, you MUST know: 1. Residency status -- resident in Japan (non-residents not covered) 2. Age -- determines pension category (20-59) and long-term care (40-64) 3. Municipality of residence -- NHI rates vary by municipality 4. Prior-year income -- NHI premiums based on prior calendar year 5. Number of NHI-enrolled household members -- per-capita component per person 6. Whether enrolled in any employer health insurance -- employees on shakai hoken excluded from NHI 7. Whether any pension exemption or deferral has been granted. If the client is enrolled in employer-based health insurance, STOP. This skill covers NHI only. (Section 2 -- Required inputs and refusal catalogue)

Refusal catalogue

• R-JP-SI-1 -- Disability pension — Disability pension eligibility and computation under the National Pension Act require case-specific assessment. Please escalate to a social insurance labour consultant. (Trigger: client asks about disability pension eligibility or computation.) (Refusal catalogue)
• R-JP-SI-2 -- Survivors pension — Survivors pension claims are outside this skill's scope. Please escalate to a social insurance labour consultant. (Trigger: client asks about survivors pension.) (Refusal catalogue)
• R-JP-SI-3 -- Voluntary additional pension (Kokumin Nenkin Kikin) — Voluntary additional pension schemes require separate analysis. Please escalate to a qualified professional. (Trigger: client asks about additional pension schemes.) (Refusal catalogue)

Section 3 -- Payment pattern library

This is the deterministic pre-classifier for bank statement entries related to social insurance. Match by case-insensitive substring.

3.1 National Pension debits

National Pension debits pattern table

Pattern	Treatment	Notes
NENKIN, PENSION, 年金, 国民年金	NATIONAL PENSION PAYMENT	Monthly premium -- due by end of following month
JAPAN PENSION SERVICE, 日本年金機構	NATIONAL PENSION PAYMENT	Same
年金前納, ADVANCE PENSION	ADVANCE PENSION PAYMENT	6-month, 1-year, or 2-year advance payment (discounted)

3.2 NHI premium debits

NHI premium debits pattern table

Pattern	Treatment	Notes
NHI, 国民健康保険, 国保, KOKUMIN KENKO	NHI PREMIUM PAYMENT	Municipal billing -- typically June to March (10 instalments)
市区町村, CITY OFFICE, WARD OFFICE	POSSIBLE NHI PAYMENT	Verify -- municipalities bill NHI directly
口座振替 (bank debit) + municipal name	NHI AUTO-DEBIT	Auto-debit for NHI premium

3.3 Long-term care (embedded in NHI for ages 40-64)

Long-term care pattern table

Pattern	Treatment	Notes
介護保険, LONG-TERM CARE	LTCI COMPONENT	Included in NHI billing for ages 40-64; separate billing for 65+

3.4 Employer health insurance (exclusion trigger)

Employer health insurance pattern table

Pattern	Treatment	Notes
健康保険, KENPO, 協会けんぽ	EMPLOYER HEALTH INSURANCE	Client is on shakai hoken -- STOP, NHI skill does not apply
厚生年金, KOSEI NENKIN	EMPLOYEES PENSION	Client is on shakai hoken -- STOP

Section 4 -- National Pension rules

4.1 Category 1 insured (Tier 1)

• Category 1 insured definition — Self-employed individuals, freelancers, students, and unemployed aged 20-59 are Category 1 insured. Monthly premium for FY 2025: JPY 17,510. Annual total: JPY 210,120. (National Pension Act, Art. 87)

4.2 Payment methods and discounts (Tier 1)

Payment methods and discounts

Method	Discount
Monthly	None
6-month advance	~1%
1-year advance	~2%
2-year advance	~4%
Bank transfer (early debit)	Slight additional discount

4.3 Tax deductibility (Tier 1)

• National Pension tax deductibility — National Pension premiums are fully deductible as social insurance premium deduction on the income tax return. No cap. (4.3 Tax deductibility (Tier 1))

4.4 Exemptions and deferrals (Tier 1 / Tier 2)

Exemptions and deferrals table (National Pension Act, Art. 90)

Exemption Type	Income Threshold (single, approx)	Payment
Full exemption	Prior-year income <= JPY 670,000	JPY 0
3/4 exemption	Income <= ~JPY 930,000	1/4 of standard
1/2 exemption	Income <= ~JPY 1,410,000	1/2 of standard
1/4 exemption	Income <= ~JPY 1,890,000	3/4 of standard
Payment deferral (under 50)	Income <= JPY 670,000	Deferred

• Exemption/deferral consequence — Exemption/deferral reduces future pension benefits. Flag for reviewer if client qualifies. (National Pension Act, Art. 90)

Section 5 -- NHI computation

5.1 NHI computation template (Tier 2)

Because rates vary by municipality, this is a template. Actual rates must be obtained from the client's municipal office.

NHI computation steps

Step	Action
5.1	Obtain prior calendar year total income
5.2	Subtract base deduction: JPY 430,000 to get NHI taxable income
5.3	For each component (Medical, Support, Long-term care): multiply by municipal income-based rate
5.4	Add per-capita amount x number of NHI-enrolled household members
5.5	Add per-household flat amount (if municipality charges it)
5.6	Cap each component at statutory maximum
5.7	Sum all three components = annual NHI premium
5.8	Divide by number of instalments (typically 10)

5.2 Illustrative rates -- Tokyo 23 Wards (Tier 2)

Illustrative rates Tokyo 23 Wards

Component	Income Rate	Per-Capita	Per-Household
Medical	~7.17%	~JPY 42,100	JPY 0
Support	~2.42%	~JPY 14,400	JPY 0
Long-term care	~2.14%	~JPY 15,600	JPY 0

These rates are illustrative. Always verify with the specific municipality.

5.3 Low-income reduction (Tier 1)

• Low-income reduction scope — Reductions apply only to per-capita and per-household portions, NOT to income-based portion. The 70%/50%/20% reductions are applied automatically based on household income reported to the municipality. (5.3 Low-income reduction (Tier 1))

Section 6 -- Payment schedules

6.1 NHI (Tier 1)

NHI payment schedule

Detail	Value
Payment period	Typically June to March (10 instalments)
Due date	End of each month (varies by municipality)
Methods	Bank transfer, convenience store, credit card, bank debit

6.2 National Pension (Tier 1)

National Pension payment schedule

Detail	Value
Payment period	Monthly, April to March
Due date	End of the following month
Methods	Bank transfer, convenience store, credit card, Pay-easy, bank debit

Section 7 -- Edge case registry

EC1 -- Mid-year arrival in Japan (Tier 2)

Situation: Client registers as resident in September. Resolution: NHI prorated from month of registration. Pension owed from month of gaining Category 1 status. Prior-year income may be zero, resulting in low NHI and possible pension exemption. Flag for reviewer.

EC2 -- Dual income: self-employment + part-time employment (Tier 1)

Situation: Client works part-time (under shakai hoken threshold) and freelances. Resolution: If part-time does not provide shakai hoken, client remains on NHI. Both employment and self-employment income included in NHI calculation. Pension remains Category 1.

EC3 -- Client turns 40 during year (Tier 1)

Situation: Client turns 40 in October. Resolution: Long-term care component starts from the month the client turns 40. NHI premium recalculated mid-year.

EC4 -- Client turns 60 during year (Tier 1)

Situation: Client turns 60 in March. Resolution: Category 1 obligation ends the month before turning 60. May optionally continue as voluntary insured. Escalate for advice on voluntary continuation.

EC5 -- Client has high income but few assets (Tier 1)

Situation: Freelancer earns JPY 10,000,000. Resolution: Income-based portion will be high, but each component is capped. Total NHI cannot exceed JPY 1,060,000.

EC6 -- Non-payment consequences (Tier 1)

Situation: Client has not paid NHI for 12 months. Resolution: Municipality may issue short-validity insurance card or qualification certificate requiring 100% upfront payment. Pension non-payment reduces future benefits and may affect disability pension eligibility.

Section 8 -- Reviewer escalation protocol

When a Tier 2 situation is identified:

REVIEWER FLAG
Tier: T2
Client: [name]
Situation: [description]
Issue: [what is ambiguous]
Options: [possible treatments]
Recommended: [most likely correct treatment and why]
Action Required: Qualified professional must confirm before advising client.

When a Tier 3 situation is identified:

ESCALATION REQUIRED
Tier: T3
Client: [name]
Situation: [description]
Issue: [outside skill scope]
Action Required: Do not advise. Refer to qualified professional. Document gap.

Section 9 -- Test suite

Test 1 -- Standard freelancer, mid-range income (Tokyo 23 Wards illustrative)

Input: Age 35, single, prior-year income JPY 5,000,000, no other household NHI members. Expected output: NHI taxable income = 5,000,000 - 430,000 = JPY 4,570,000. Medical: ~JPY 369,769. Support: ~JPY 124,994. Long-term care: N/A (under 40). Total NHI: ~JPY 494,763. Pension: JPY 210,120. Total: ~JPY 704,883.

Test 2 -- Low-income freelancer qualifying for 70% reduction

Input: Age 28, single, prior-year income JPY 300,000. Expected output: NHI taxable income = JPY 0. Income-based = JPY 0. 70% reduction on per-capita. Medical per-capita: JPY 12,630. Support: JPY 4,320. Total NHI: ~JPY 16,950. Pension: full exemption likely.

Test 3 -- High earner hitting caps

Input: Age 45, single, prior-year income JPY 20,000,000. Expected output: Medical capped at JPY 650,000. Support capped at JPY 240,000. Long-term care capped at JPY 170,000. Total NHI: JPY 1,060,000. Pension: JPY 210,120. Total: JPY 1,270,120.

Test 4 -- Mid-year registration

Input: Age 30, registers residency in July (9 months). Expected output: NHI prorated x 9/12. Pension: JPY 17,510 x 9 = JPY 157,590.

Section 10 -- Prohibitions and disclaimer

Prohibitions

• Prohibitions list — - NEVER assume NHI rates are uniform across Japan -- they vary by municipality and MUST be verified - NEVER omit the long-term care component for clients aged 40-64 - NEVER include clients enrolled in employer shakai hoken in NHI calculations - NEVER treat National Pension as optional for Category 1 insured persons aged 20-59 -- it is legally mandatory - NEVER forget that NHI premiums are based on PRIOR-year income, not current-year income - NEVER apply the low-income reduction to the income-based portion -- it applies only to per-capita and per-household portions - NEVER present calculations as definitive -- always label as estimated and direct client to their municipal office or a qualified professional (Prohibitions)

Disclaimer

This skill and its outputs are provided for informational and computational purposes only and do not constitute tax, legal, or financial advice. Open Accountants and its contributors accept no liability for any errors, omissions, or outcomes arising from the use of this skill. All outputs must be reviewed and signed off by a qualified professional (such as a tax accountant, social insurance labour consultant, or equivalent licensed practitioner in Japan) before filing or acting upon.

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