Japan: per-date 80%→70% input-tax credit, national ¥106,314 and −¥11,622 against all-80% on the sample. Germany: Midijob 1.000 € employee share 125,33 €, bases 854,06 € / 568,36 €, factor F 0.6619.
The same files run in Claude (claude.ai, Claude Code), ChatGPT Business, Codex and Gemini CLI.

What you get
• jp-invoice-transition-2026: Japan’s transitional input-tax credit by purchase date, per-supplier cap, small-amount rule
• de-midijob-2026: German Minijob and Midijob social insurance with the 2026 values
• Each with a dated rule table, official sources and the real example output

Install
claude.ai: Customize → Skills → Upload skill (turn on code execution under Capabilities). ChatGPT Business: Skills → Create → Upload. Claude Code: unzip into ~/.claude/skills/. Needs Python 3.8+.

What it does not do
Offline – nothing is sent anywhere. Wage-tax withholding and some fund-specific levies are out of scope (each README lists them).
Calculation aids, not tax or payroll advice – have a tax adviser or payroll office confirm.

FAQ
Q: How is this different from asking the assistant directly?
A: Each skill carries a dated rule table and a script, so the assistant computes with the official formula instead of answering from memory.
Q: Files
A: After paying, open it in your Whop library: “Download — jp-invoice-transition-2026”, “Download — de-midijob-2026” each have a lesson with that skill’s zip attached.