Methodology & sources

A trustworthy calculator must make its assumptions completely transparent. This page documents the mathematical models, primary government sources, and software testing protocols behind SalarySteps.

Primary Statutory Sources (Tax Year 2026)

All calculations on this site are calibrated to official figures published by federal and state revenue authorities:

• Federal Tax Brackets & Standard Deductions: IRS Revenue Procedure 2025-32 (annual cost-of-living adjustments for tax year 2026). Standard deductions: Single $16,100; Married Filing Jointly $32,200; Head of Household $24,150.
• Social Security Taxable Wage Base: Social Security Administration 2026 COLA Fact Sheet setting the maximum taxable earnings limit at $184,500 for the 6.2% Old-Age, Survivors, and Disability Insurance (OASDI) tax.
• Medicare Payroll Tax: Federal Insurance Contributions Act (FICA) establishing the 1.45% Medicare tax rate with no wage cap, and the Affordable Care Act (ACA) 0.9% Additional Medicare tax on single incomes exceeding $200,000.
• Supplemental Wage Withholding: IRS Publication 15-A (Employer's Supplemental Tax Guide), establishing the flat 22% federal withholding rate for bonuses and supplemental wages under $1,000,000.
• Overtime & Wage Standards: U.S. Department of Labor Fair Labor Standards Act (FLSA), 29 U.S.C. § 207, governing the standard 40-hour workweek and statutory 1.5x regular rate overtime compensation.

Calculation Architecture & Parity Auditing

To provide instant, interactive calculation speeds without sacrificing mathematical rigor, SalarySteps uses an audited dual-engine pipeline:

1. Python Reference Engine: Pure Python functions define the canonical mathematical implementation, tested with pytest across dozens of verified baseline test vectors.
2. Client-Side Engine: An optimized JavaScript engine mirrors the Python logic directly in the visitor's browser, ensuring absolute data privacy.
3. Zero-Tolerance Pre-Deploy Audit: The ToolForge build system automatically executes both engines against identical test suites. If any calculation differs by more than $0.0001, the deploy is aborted.

Core Assumptions & Modeling Limits

Unless explicitly configured otherwise on a specific calculator, our baseline calculations assume:

• A single tax filer claiming the statutory standard deduction with zero dependents.
• A standard full-time work schedule of 40 hours per week for 52 weeks per year (2,080 annual hours).
• Exclusion of employer-specific pre-tax benefit elections (such as 401(k) contributions, HSA/FSA deferrals, and health insurance premiums) and post-tax garnishments.
• Divide-by-frequency payroll conventions: annual tax obligations divided by 26 for biweekly schedules, 24 for semi-monthly schedules, and 52 for weekly schedules.

Questions & Source Verification

Questions regarding our mathematical models or requests for custom verification should be directed to [email protected].