NISA Calculator: Japan

🇯🇵 Master Japan's New NISA & iDeCo Tax-Advantaged Wealth Creation — 100% Offline & Private!

NisaMaster JP is the definitive compound growth and statutory tax exemption simulator engineered specifically for Japan's Financial Services Agency (FSA) New NISA and National Tax Agency (NTA) iDeCo legal frameworks.

Whether you're planning monthly DCA (Tsumitate), maximizing the ¥18,000,000 lifetime holding limit, calculating statutory 20.315% capital gains tax savings, or planning your retirement roadmap to FIRE, NisaMaster JP gives you immediate, transparent financial intelligence.

🌟 KEY FEATURES:

1. 📊 New NISA Lifetime Limit & Tax Savings Engine
• Dual Concentric Ring Gauges displaying real-time utilization of the total ¥18,000,000 Lifetime Quota and ¥12,000,000 Growth Sub-Quota.
• Combined DCA (¥100k/mo, ¥1.2M/yr) and Growth Quota (¥2.4M/yr) simulation up to the ¥3.6M annual ceiling.
• Household modes: Single (¥18M), Married Couple (¥36M), and Family (¥54M).
• Exact 20.315% tax savings calculation (15% National + 0.315% Reconstruction Surtax + 5% Local Resident Tax) vs. standard taxable accounts (Tokutei Kouza).
• Next-Year Book Value Restoration Simulator upon selling positions.

2. 📈 3-Scenario Investment Matrix
• Compare Conservative (3.0%), Balanced (5.0% All-Country World Index), and Aggressive (8.0% S&P 500) side-by-side.
• Instant visibility into final portfolio values, cumulative principal, capital gains, tax saved, and delta gains.

3. ⏳ Age-to-FIRE Reverse Target Calculator
• Reverse Annuity Calculation: Input your dream nest egg (e.g. ¥50,000,000) and target retirement age to calculate required monthly savings.
• Automated check whether your monthly contribution fits inside the legal NISA cap (¥300,000/mo).
• Safe 4% Withdrawal Rule simulator for annual & monthly retirement income.

4. 🏛️ iDeCo Salary Waterfall & Tax Deduction Suite
• Dynamic employment tier support: Tier 1 (Self-employed ¥68k), Tier 2 (Corporate employee ¥12k-¥23k, Civil servant ¥12k), Tier 3 (Dependent spouse ¥23k).
• Full tax waterfall: Employment income deduction, social insurance estimation, basic exemption (¥480,000), marginal income tax rate (5%-45%), and local inhabitant tax (10%).
• Clear yearly income tax refund and resident tax savings summary.

5. 💳 Credit Card Point Rebate Simulator
• Model major Japan brokerage card rebates (0.5% to 5.0% on SBI, Rakuten, Monex).
• Compound long-term point reinvestment compounding over 10-30 years.

6. 📤 RFC-4180 CSV Export
• Export year-by-year amortization schedules with UTF-8 BOM encoding for seamless opening in Microsoft Excel or Google Sheets.

🔒 PRIVACY FIRST & OFFLINE:
• 100% On-Device execution. No servers, no tracking, no analytics.
• Zero account creation or personal login required.
• Your financial data stays strictly on your phone.