Free Agent Tools

Leaving Japan: which resident tax (住民税) years are still owed, is a tax agent (納税管理人) needed, and what are the income-tax and move-out deadlines?

japan_leaving_tax_check

Read-onlyIdempotent

Checks what tax and paperwork are still due when someone leaves Japan, from the Local Tax Act (地方税法 39 / 294 / 300 / 318 / 321-5), Income Tax Act (所得税法 126 / 127 / 190), 国税通則法 117, 住民基本台帳法 24, MIC resident-tax pages, NTA Tax Answers 1920 / 1923 / 1926 / 1478 and the Japan Pension Service, rules as of 2026-11-01. Resident tax (住民税) is assessed on whoever is registered in a city on January 1, on the previous year's income, for the fiscal year June–May: leave (with a 転出届) on or before December 31 → no next-year 住民税; leave January 2 or later → that fiscal year is owed in full. Leaving January–May, the bill is issued mid-June after departure → tax agent (納税管理人) needed (or settle / city certification). Payroll deduction (特別徴収): job ending January 1 – April 30 → remaining installments taken as a lump sum from the final pay (mandatory); June–December → only on request. Income tax: year-end adjustment on the last salary before departure; if a return is needed, 準確定申告 by the departure date, or by March 15 next year via a tax agent notified to the tax office; previous year's return due by departure when leaving January 1 – March 15; exit-tax flag for ¥100M+ securities. Also the 転出届 window (~14 days before), pension Lump-sum Withdrawal claim deadline (2 years) and residence card. plan: leave (a year or more) | short (trip under a year → still resident). Returns verdict (agent_needed | settle_before_departure | nothing_after_departure | still_resident), summary, residentTax {fiscalYears [{fiscalYear, incomeYear, status owed | not_owed | check_with_city, why, howToPay}], nextFiscalYearAvoided, leaveByToAvoidNextFY, jan1Tip, lumpSumFromFinalPay, agentRequired, agentForm}, incomeTax {yearEndAdjustment, returnRequired, returnDeadline, previousYearReturnDeadline, agentRequired, agentForm, exitTax}, deadlines [{date, what, ja, mandatory, passed}], actions, warnings, pension {lumpSumClaimBy}, sources, disclaimer. No yen amounts. Use for 'leaving Japan resident tax', 'do I pay juminzei after leaving Japan', '住民税出国 1月1日', '納税管理人必要', 'leave Japan before December 31 tax', 'final salary resident tax lump sum', '準確定申告出国'. Educational, not tax or legal advice; not affiliated with the NTA, MIC, any city office or the Japan Pension Service.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "departureDate": "<departureDate>"
    },
    "name": "japan_leaving_tax_check"
  }
}

Input Schema

Name	Required	Description
`plan`	No	leave (moving abroad for a year or more, files a 転出届; default) \| short (trip under a year, keeps the address).
`today`	No	Override today's date (default: today in Japan).
`payMethod`	No	How 住民税 is paid: salary (payroll, 特別徴収) \| self (bills, 普通徴収) \| none. Default from employment.
`employment`	No	employee (default) \| self_employed \| none.
`jobEndDate`	No	Job end date (default: departureDate); decides the final-salary lump-sum rule.
`arrivalDate`	No	When you first registered an address in Japan (default: before January 1 of the departure year).
`hasTaxAgent`	No	Will appoint a tax agent (納税管理人).
`nationality`	No	foreign (default) \| japanese (pension lump sum / residence card only for foreign nationals).
`departureDate`	Yes	The day you leave Japan, YYYY-MM-DD.
`pensionMonths`	No	Months of Japanese pension contributions (6–119 → lump-sum claim deadline).
`incomeLastYear`	No	Had taxable income last calendar year (default true).
`needsTaxReturn`	No	Needs an income tax return this year (side income > ¥200k, salary > ¥20M, self-employed, two employers…). Default: true only for self_employed.
`securities100M`	No	Holds ¥100M+ in securities etc. → exit-tax (国外転出時課税) flag.
`incomeAfterLeaving`	No	Japan-source income after leaving (rent, property sale) → tax agent needed.
`prevYearReturnPending`	No	Leaving January 1 – March 15 with last year's return not yet filed.

Schema Changelog

Changes observed during successful MCP inspections.

AddedNov 1, 2026

TDQS

A4.3/5.0

Behavior4/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the bar is lower. The description still adds real value: rules pinned to an as-of date (2026-11-01), the explicit 'No yen amounts' output constraint, the educational/not-advice disclaimer, and a non-affiliation statement. It also spells out the rules engine's logic (Jan 1 registration, June–May fiscal year, lump-sum clawback windows), which annotations cannot convey.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness3/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Purpose and the core January-1 rule are front-loaded, and the closing return-shape list is useful. But the statutory citation string (地方税法 39 / 294 / 300 / 318 / 321-5, 所得税法 126 / 127 / 190...) is dense, low-actionability noise for an agent, and the middle section is a single run-on paragraph of overlapping deadlines that would be clearer as a list.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a 15-parameter, no-output-schema tool, the description is unusually complete: it enumerates every return field (verdict enum values, residentTax.fiscalYears structure, deadlines, pension, sources, disclaimer) so an agent knows what comes back without an output schema, and it pins the rule set to a date. Nothing an agent needs to call or interpret this tool is missing.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100% and four enums are self-documented, so baseline is 3. The description goes further by tying parameters to their consequences (payMethod → 特別徴収 rules, jobEndDate → final-salary lump sum, nationality → pension lump-sum eligibility) and by explaining the leave/short plan distinction in the context of residency, which helps an agent set inputs correctly rather than guess defaults.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The opening clause names a specific verb and scope: 'Checks what tax and paperwork are still due when someone leaves Japan', and then enumerates the exact sub-domains (resident tax years, 納税管理人, income-tax deadlines). This is clearly distinguishable from the sibling Japan tools (visa fee, reentry deadline, permanent residency), which cover different question types.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description ends with an explicit trigger-phrase list ('leaving Japan resident tax', 'do I pay juminzei after leaving Japan', '納税管理人必要', '準確定申告出国'), which gives an agent a precise matching signal. It does not state when NOT to use it or name overlapping siblings (e.g. japan_reentry_deadline_check shares the 転出届 ~14-day window), so routing at the margin is inferred rather than stated.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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