Calculation Method and Update Policy

Independent implementation approach

• Calculators are built inside the HibiCalc project using public formulas, rules, and required inputs. HibiCalc does not call official systems from government agencies, banks, or transport operators.
• Flow: read inputs in the browser, compute, apply rounding rules, and render the result on the same page.

Source hierarchy

• For areas with legal changes or provider-specific differences, official public publications are reviewed first.
• We prioritize materials from the National Tax Agency, Japan Pension Service, Ministry of Health, Labour and Welfare, transport operators, and official lenders.

• Tax and withholding: latest NTA, customs, and local authority publications
• Pensions and benefits: Japan Pension Service, MHLW, and provider guidance
• Transportation and refunds: official rules from the operator used
• Loan and finance: lender’s repayment schedule and contract terms

Your own records and period-specific rules determine final values; verify before using for official actions.

Validation model

1. Define the purpose, inputs, units, and allowed options for each calculator.
2. Implement input checks, calculations, rounding, and output breakdowns from public formulas.
3. Validate boundary cases such as zero values, date changes, period changes, and category switches.
4. Flag estimates and non-coverage conditions on each calculator screen.

CSV or table output is useful for workflow, but it is not an official form or contract document.

About estimates and exclusions

Results are for comparison and preparation only. Differences can occur due to legal timing, rounding behavior, regional rules, company rules, and individual contract terms.

For filing, payment, application, payroll processing, loan contracts, or refund claims, use official material from the relevant authority and use HibiCalc only as a reference.

Updates and issue handling

• When rules or rates change, we review formulas, options, labels, and notes on affected pages.
• Not every legal change can be mirrored instantly. Always check the page period and displayed caution notices.
• If you find a calculation error or broken link, please report it with the exact page and reproduction conditions.

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