Methodology & data sources
Every Treasury.to calculator runs on official data from the issuing authority and standard finance formulas. This page lists exactly which source powers which calculator, when each was last verified, and how we update when laws change.
Updated:
§ 01
Tax data by country
| Topic | Data | Official source | Verified |
|---|---|---|---|
| US federal income tax (income-tax-us) | 7 marginal brackets × 4 filing statuses, standard deduction, 2026 inflation adjustments | IRS Rev. Proc. 2025-32 ↗ | 2026-05 |
| Vietnam personal income tax (salary-vn) | 7-bracket PIT schedule, family circumstance deductions, 2026 thresholds | Nghị quyết 110/2025/UBTVQH15 (Ủy ban Thường vụ Quốc hội) ↗ | 2026-05 |
| Vietnam social insurance (salary-vn) | BHXH 8%, BHYT 1.5%, BHTN 1% employee; caps tied to base salary | Luật Bảo hiểm xã hội 2024 + Nghị định hướng dẫn ↗ | 2026-05 |
| Brazil IRRF (salary-br) | Progressive table, R$5,000 exemption + gradual reduction up to R$7,350, INSS 7.5/9/12/14% | Receita Federal, Lei 14.973/2024 + MP 1.171/2024 ↗ | 2026-05 |
| France income tax (salary-fr) | Barème IR 0/11/30/41/45 %, quotient familial, cotisations sociales ~22%, déduction 10% | Service-public.fr / loi de finances 2026 ↗ | 2026-05 |
| Indonesia PPh 21 (salary-id) | 5/15/25/30/35% brackets, PTKP by status, biaya jabatan 5% (capped), BPJS ~4% | DJP / PP 58/2023 ↗ | 2026-05 |
| Spain IRPF (salary-es) | IRPF 19/24/30/37/45/47%, Seguridad Social ~6.50% (capped, incl. MEI), personal & family minimum | Agencia Tributaria (AEAT) 2026 ↗ | 2026-05 |
§ 02
Market data
| Topic | Data | Official source | Verified |
|---|---|---|---|
| Live market ticker (15 symbols) | Indices, FX, commodities, US 10Y yield, crypto — 60-second cache | Yahoo Finance chart endpoint (unofficial public API) ↗ | 2026-05 |
§ 03
Financial formulas
| Topic | Data | Official source | Verified |
|---|---|---|---|
| FIRE calculator — 4% safe withdrawal rate (fire) | 60/40 stocks/bonds portfolio supports 4% inflation-adjusted withdrawals for 30 years at high success rate | Trinity Study — Cooley, Hubbard, Walz (1998, updated 2011, 2020) ↗ | 2026-05 |
| Compound interest (compound-interest) | FV = P(1 + r/n)^(n·t) + PMT · [((1 + r/n)^(n·t) − 1) / (r/n)] across 11 compounding frequencies | Standard time-value-of-money closed form ↗ | 2026-05 |
| Mortgage P&I + amortization (mortgage) | M = P · [r(1+r)^n] / [(1+r)^n − 1] · with month-by-month principal/interest split | Standard mortgage amortization formula ↗ | 2026-05 |
| Affordability (affordability) | 28/36 debt-to-income rule, US convention; ratios applied to gross monthly income | Consumer Financial Protection Bureau guidance ↗ | 2026-05 |
§ 04
Update cadence
After any new tax authority release (IRS Rev. Proc., NQ UBTVQH, Receita Federal, DJP, AEAT, loi de finances), we re-verify within 30 days and bump the 'Last verified' stamp. Market quotes come from Yahoo Finance with a 60-second cache — no fallback values; if the source fails, the ticker hides itself.
§ 05
Disclaimer
Treasury.to produces estimates for personal planning. Not tax, investment, or legal advice. Consult a qualified professional in your jurisdiction before making material financial decisions.