income-tax

income-tax is a skill for Claude Code from kazukinagata/shinkoku. It costs 114 tokens per session (11,669 once invoked), scanned A, original, MIT.

A workflow for calculating Japanese income tax, deductions, refunds, and payment amounts from income records. It assumes the related blue-return financial statements have already been completed.

In plain words
What is it for?
Use it to calculate taxable income, deductions, income tax, reconstruction special income tax, payment amounts, or refunds, and prepare values for tax forms.
Why use it?
It organizes the tax calculation steps and applies the specified rounding rules before figures are entered into Japan's online tax filing system.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin. Also seen: names the AskUserQuestion tool.

Not installable: its command points at a path on the author’s own machine, so it runs nowhere else. The line is /home/user/tax-2025/.

Part of the shinkoku plugin — 24 skills shipped together

Good fit Use it to calculate taxable income, deductions, income tax, reconstruction special income tax, payment amounts, or refunds, and prepare values for tax forms.

Compare 6 skills from other repositories ↓
Install

Getting it into your agent

This one installs as part of its plugin. Adding the marketplace and installing the plugin brings it with everything else the plugin ships.

Claude Code
/plugin marketplace add kazukinagata/shinkoku
Claude Code
/plugin install shinkoku

Made for: Claude Code.

Or install shinkoku, the plugin that ships this one along with the rest of its 24 skills.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for income-tax

README.md
[![agentmods](https://agentmods.dev/badge/skills/kazukinagata/shinkoku/income-tax/github.svg)](https://agentmods.dev/skills/kazukinagata/shinkoku/income-tax)
Your own site
<a href="https://agentmods.dev/skills/kazukinagata/shinkoku/income-tax"><img src="https://agentmods.dev/badge/skills/kazukinagata/shinkoku/income-tax/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for income-tax

Your own site · 80×15
<a href="https://agentmods.dev/skills/kazukinagata/shinkoku/income-tax"><img src="https://agentmods.dev/badge/skills/kazukinagata/shinkoku/income-tax.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 114 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 11,669 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • Socket pass 18 Mar 2026
  • Snyk pass 7 Mar 2026
How audits are shown
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00114 $0.11669
Opus 5 $0.00057 $0.05835
Sonnet 5 $0.00023 $0.02334
Haiku 4.5 $0.00011 $0.01167

Measured 2d ago against content hash 21621328c3d2, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

income-tax scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skills/income-tax/SKILL.md · 873 lines

How it starts

The opening of the file, as written. The whole thing — 873 lines — stays where its author put it; the contents beside it link to each section on GitHub.

所得税計算(Income Tax Calculation)

事業所得・各種控除から所得税額を計算するスキル。 settlement スキルで決算書の作成が完了していることを前提とする。 計算結果は /e-tax スキル(Claude in Chrome)で確定申告書等作成コーナーに入力する。

設定の読み込み(最初に実行)

  1. shinkoku.config.yaml を Read ツールで読み込む
  2. ファイルが存在しない場合は /setup スキルの実行を案内して終了する
  3. 設定値を把握し、相対パスは CWD を基準に絶対パスに変換する:
    • db_path: CLI スクリプトの --db-path 引数に使用
    • output_dir: 進捗ファイル等の出力先ベースディレクトリ
    • 各ディレクトリ: ファイル参照時に使用

パス解決の例

config の db_path./shinkoku.db で CWD が /home/user/tax-2025/ の場合:

  • shinkoku tax calc-income --input /home/user/tax-2025/output/income_input.json

進捗情報の読み込み

設定の読み込み後、引継書ファイルを読み込んで前ステップの結果を把握する。

  1. .shinkoku/progress/progress-summary.md を Read ツールで読み込む(存在する場合)
  2. 以下の引継書を Read ツールで読み込む(存在する場合):
    • .shinkoku/progress/06-settlement.md
    • .shinkoku/progress/02-assess.md
    • .shinkoku/progress/05-furusato.md
  3. 読み込んだ情報を以降のステップで活用する(ユーザーへの再質問を避ける)
  4. ファイルが存在しない場合はスキップし、ユーザーに必要情報を直接確認する

基本方針

  • settlement スキルで青色申告決算書が完成しているか確認してから開始する
  • 所得の計算 → 控除の計算 → 税額の計算 の順序で進める
  • 各ステップの計算結果をユーザーに提示し、確認を得る
  • references/form-b-fields.md の各欄に正しく値を設定する
  • 端数処理ルールを厳守する:
    • 課税所得: 1,000円未満切捨て(国税通則法118条)
    • 復興特別所得税: 1円未満切捨て(復興財源確保法13条)
    • ㊺ 所得税及び復興特別所得税の額: 端数処理なし
    • 申告納税額(納付の場合のみ): 100円未満切捨て(国税通則法119条)
    • 還付金: 1円単位・切捨てなし(国税通則法120条)

前提条件の確認

所得税計算を開始する前に以下を確認する:

  1. 青色申告決算書が完成しているか: settlement スキルの出力を確認する
  2. 納税者プロファイルの読み込み: uv run shinkoku profile --config {config_path} で config から納税者情報を取得する
    • 氏名・住所・税務署名 → 確定申告書等作成コーナーへの入力に使用
    • 寡婦/ひとり親・障害者・勤労学生の状態 → 人的控除の計算に使用
  3. 事業所得以外の所得: 給与所得・雑所得・配当所得・一時所得等がある場合は情報を収集する
  4. 源泉徴収票: 給与所得がある場合は取り込みを案内する
  5. 各種控除の適用状況: 適用可能な控除を網羅的に確認する
  6. 予定納税額: assess で確認済みの予定納税額を取得する
    • 未確認の場合は、前年の確定申告書(㊺欄)から判定する
    • 予定納税額は源泉徴収税額とは別に管理する
  7. 分離課税の確認: 株式・FX の分離課税(第三表)は対象外。該当する場合は税理士への相談を案内する

必須確認チェックリスト(スキップ不可)

所得税計算を開始する前に、以下の項目がすべて確認済みであることを検証する。 config・引継書に記載がない項目は、ユーザーに直接確認してから先に進む。

  • 家族構成: 配偶者の有無・扶養親族の有無を確認済みか?
    • 未確認 → ユーザーに確認し、ステップ1.5 で詳細を登録する
    • 確認済み(該当なし)→ ステップ1.5 をスキップ可
  • 住宅ローン控除: 適用有無を確認済みか?
    • 未確認 → ユーザーに確認する
    • 適用あり(初年度)→ ステップ3.7 で明細書を作成する
  • 予定納税: 有無・金額を確認済みか?
    • 未確認 → 前年の確定申告書(㊺欄)から判定するようユーザーに確認する
    • 金額未確定 → estimated_tax_payment パラメータに正しい値を設定できるまで進まない

Read the full file on GitHub · 873 lines

Files

What ships with it

4 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago Changed 21621328c3d2
  2. 12d ago First seen · 873 lines · 114 tokens per session scan A c2211e90f7f1

Subscribe to this mod's changes

income-tax is a skill published in the GitHub repository kazukinagata/shinkoku (359 stars, last pushed 3d ago), licensed MIT. It adds 114 tokens to every session and 11,669 once invoked, about $0.0006 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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