# Estimate Japanese Monthly Withholding Tax

Japanese salary withholding varies with payment year, eligible dependents, and pay after social insurance. This skill calculates local formula-based estimates and explains differences from printed tax tables.

## Install

```bash
npx skillstore add tahodev/withholding-tax
```

## Metadata

- Status: approved
- Slug: tahodev-withholding-tax
- Skillstore revision: r1
- Version status: missing
- Tree hash: 517fa7f41939ce823da127ff99c4c32f8949604221db91cf62e096bdadace35f
- Author: tahodev
- GitHub username: tahodev
- License: MIT
- Repository: https://github.com/tahodev/kurashi-skill/tree/09cb7f9eac85f0c85633cce08328a1a57854a94f/withholding-tax
- Ref: 7f17813fb6af1acc7d8fd3fb5f05480f5be52783
- Supported tools: Claude, Codex, Claude Code
- Audit status: complete
- Agent install advisory: allowed
- Manual install advisory: allowed
- Artifact signature: available
- Audit attestation: unavailable
- Human verification: not\_verified
- Risk factors: external\_commands, network
- Quality score: 77
- Quality tier: bronze
- Public page: https://skillstore.pages.dev/skills/tahodev-withholding-tax
- Manifest: https://skillstore.pages.dev/api/skills/tahodev-withholding-tax/manifest

## Capabilities

- Estimate monthly column A income-tax withholding from salary after social insurance and eligible dependent counts.
- Apply separate bundled deduction constants for 2026 and 2027 payment years.
- Show employment-income deductions, dependent deductions, basic deductions, taxable income, and estimated withholding.
- Apply deduction rounding and round calculated withholding to the nearest 10 yen.
- Explain documented differences between formula estimates and printed monthly tax tables.
- Calculate locally using Python standard-library modules and reject unsupported years or negative inputs.

## Use Cases

- Check a monthly payslip estimate: Estimate withholding from salary after social insurance and compare the result with employer deductions.
- Compare payment-year assumptions: Compare 2026 and 2027 formula estimates for identical salary and dependent inputs before discussing payroll differences.
- Explain deduction calculations: Show a worked deduction breakdown and explain why formula estimates can differ from monthly tax-table amounts.

## Prompt Templates

### Get a basic estimate

```
Estimate my 2026 monthly withholding for 175,000 yen after social insurance and two eligible dependents. State the tax-table limitation.
```

### Review the deduction breakdown

```
For [year], estimate withholding on [salary] yen after social insurance with [dependents] eligible dependents. Show each deduction and the rounding.
```

### Compare supported years

```
Compare 2026 and 2027 monthly withholding estimates for 300,000 yen after social insurance and zero eligible dependents. Identify changed deductions and estimate differences.
```

### Investigate a payroll discrepancy

```
Review [year] withholding for [salary] yen after social insurance, [dependents] eligible dependents, and employer withholding of [amount] yen. Explain possible formula-versus-table differences without assuming employer error.
```

## Limitations

- Only 2026 and 2027 are supported; the calculator defaults to 2026 and does not automatically update tax rules.
- Inputs must be integer yen after social insurance and eligible dependent counts; the skill does not determine eligibility.
- Column B, bonuses, daily tables, retirement pay, resident tax, annual returns, and year-end adjustment calculations are excluded.
- Results are estimates and may differ from printed tables or employer withholding; they do not calculate total take-home pay.

## Best Practices

- Use salary after social insurance deductions, not gross salary or total take-home pay.
- Specify the payment year explicitly and confirm the eligible dependent count before calculating.
- Compare estimates with the applicable official table and employer payslip before making payroll decisions.

## Anti Patterns

- Entering gross salary as salary after social insurance.
- Treating formula estimates as exact tax-table values or final annual tax liabilities.
- Using the default 2026 year for other payment years or applying the calculator to bonuses and column B.

## Security Audit

- Audited at: 2026-10-13T04:27:43.409\+00:00
- Summary: All seven static findings are false positives: Markdown fences, official tax-reference URLs, and readable Japanese text triggered the patterns. The reviewed calculator performs local arithmetic without network calls or shell execution. No evidence found of prompt injection, credential access, or data exfiltration.

## Stats

- Views: 0
- Downloads: 0
- Favorites: 0
- Popularity score: 0