shinkoku

Automates Japanese tax returns end to end: bookkeeping, income and consumption tax, deductions, and filling in the NTA's e-Tax filing forms.

Pack · 24 skills

by kazukinagata

About

Ratings and reviews

What shinkoku does

About

A community Claude Code plugin and Agent Skills pack by Kazuki Nagata (kazukinagata) that handles the Japanese tax return (確定申告) from bookkeeping through to entering everything in the National Tax Agency's online filing forms. It's built for sole proprietors on blue-form returns, employees with side income, and salaried workers claiming refunds or deductions. The skills are written in Japanese. What you can do with it - Keep the books with journal entries, and produce the year-end settlement and financial statements - Calculate income tax and consumption tax, including the 20% special rule, simplified taxation and the standard method - Read receipts, invoices, withholding slips, payment statements and deduction certificates - Track furusato nozei donations, estimate the deduction limit and handle the one-stop exception - Work out medical expense and first-year housing loan deductions, and report crypto gains as miscellaneous income - Fill in the NTA's 確定申告書等作成コーナー through browser automation, then submit How it works - 24 skills cover the flow: assess, gather, journal, settlement, income-tax, consumption-tax, furusato, e-tax, submit and more, plus tax-law context skills. - The skills call the shinkoku CLI (installed with uv; Python 3.11 or newer). /setup installs it for you. - Install as a Claude Code plugin from the maker's own marketplace (kazukinagata/shinkoku), or add the skills with npx skills add kazukinagata/shinkoku. - Filling the e-Tax forms needs browser automation: Claude in Chrome, Antigravity's browser agent, or Playwright CLI (beta). Good to know - Covers the 2025 and 2026 tax years. Not for separately taxed stock income, FX, real-estate income, retirement income, white-form returns or non-residents. - You're responsible for your return: check everything before submitting, and ask a tax accountant if unsure. - A community project, not affiliated with the National Tax Agency.

Things to ask it

Once it’s added

“確定申告の準備を始めたい。何から必要？”
“Record this month's receipts as journal entries”
“Read this withholding slip and calculate my refund”
“How much more can I donate through furusato nozei this year?”
“Calculate my consumption tax using the 20% special rule”
“Enter my return into the e-Tax filing form”

What it can do

Before you add it

Reads only

Receipts, invoices, withholding slips and deduction certificates you provide · Your books and prior entries

Makes changes · your agent can ask first

Journal entries, settlement and tax calculations · Entries in the NTA's online filing forms, through browser automation

Skills in shinkoku

Pack · 24 skills, each with its own page

assessSecurity scan passedThis skill should be used when the user asks to determine what tax filings they need, wants to know if they must file a…
capabilitiesSecurity scan passedDisplay shinkoku's current capabilities, supported personas, and known limitations.
consumption-taxSecurity scan passedThis skill should be used when the user needs to calculate consumption tax (消費税) or determine their tax method (2割特例, 簡…
e-bookkeeping-complianceSecurity scan passed優良な電子帳簿の要件チェック・コンプライアンス診断を実行する。「優良な電子帳簿」「電帳法対応」「電子帳簿の要件確認」「税務調査の準備」「75万円控除の条件」「帳簿の要件を満たしているか」「e-bookkeeping complian…
e-taxSecurity scan passedThis skill should be used when the user wants to file their tax return electronically via the 確定申告書等作成コーナー (NTA Tax Ret…
furusatoSecurity scan passedThis skill manages furusato nozei (hometown tax) donations.
gatherSecurity scan passedThis skill should be used when the user needs to know what documents to collect for their tax filing, wants a checklist…
income-taxSecurity scan passedThis skill should be used when the user needs to calculate their income tax (所得税), compute deductions, or import withho…
incorporationSecurity scan passed法人成り（個人事業主から法人への移行）に関する相談。税額比較シミュレーション、法人形態の選択、設立手続き、役員報酬戦略、社会保険の比較を支援する。 Trigger: "法人成り", "会社設立", "法人化", "株式会社にしたい",…
invoice-systemSecurity scan passedThis skill should be used when the user asks about the invoice system (インボイス制度), qualified invoices (適格請求書), registrati…
journalSecurity scan passedThis skill should be used when the user wants to record bookkeeping entries (仕訳), import transaction data from CSV file…
reading-deduction-certSecurity scan passed控除証明書（生命保険料・地震保険料等）の画像を読み取り構造化データを返す。他のスキルから呼び出されるほか、直接ユーザーが呼び出すことも可能。
reading-invoiceSecurity scan passed請求書の画像を読み取り構造化データを返す。他のスキルから呼び出されるほか、直接ユーザーが呼び出すことも可能。
reading-payment-statementSecurity scan passed支払調書の画像を読み取り構造化データを返す。他のスキルから呼び出されるほか、直接ユーザーが呼び出すことも可能。
reading-receiptSecurity scan passedレシート・領収書・ふるさと納税受領証明書の画像を読み取り構造化データを返す。他のスキルから呼び出されるほか、直接ユーザーが呼び出すことも可能。
reading-withholdingSecurity scan passed源泉徴収票の画像を読み取り構造化データを返す。他のスキルから呼び出されるほか、直接ユーザーが呼び出すことも可能。
settlementSecurity scan passedThis skill should be used when the user needs to perform year-end closing adjustments (決算整理), review financial statemen…
setupSecurity scan passedThis skill should be used when the user wants to set up shinkoku for the first time, initialize their configuration, or…
submitSecurity scan passedThis skill should be used when the user is ready to submit their tax return, needs a final review checklist, wants to k…
tax-advisorSecurity scan passedThis skill should be used when the user asks tax-related questions, wants advice on deductions or tax savings, or needs…
tax-ebookkeeping-contextSecurity scan passedBackground context for the Electronic Bookkeeping Act (電子帳簿保存法) in the shinkoku tax filing plugin.
tax-housing-loan-contextSecurity scan passedBackground context for housing loan tax credit (住宅ローン控除) in the shinkoku tax filing plugin.
tax-invoice-credit-contextSecurity scan passedBackground context for invoice-system input tax credit rules (仕入税額控除) in the shinkoku tax filing plugin.
tax-legal-contextSecurity scan passedBackground legal and regulatory context for the shinkoku tax filing plugin.

Install shinkoku

Your agent

Runs on your machine.

In ChatGPTDownload the shinkoku folder and zip it, then Plugins → Skills → Create → Upload from your computer. Business and Enterprise plans.

View the skills on GitHub

Runs on your machine.