Sales Tax Compounding and Reverse
Pre-tax / post-tax / tax with combined state + local rate.
Example
You enter
- Pre-tax amount (USD) 1000
- Rate 1 (state, percent) 6.25
- Rate 2 (local, percent) 1.5
You get
- Tax $77.5
- Post tax 1077.5
- Combined rate (%) 7.75
Checked against published worked examples from: OpenStax, Rice University.
Details, formula, and sources
ScopeReverse from a receipt total.
Formula or tableForward: tax = pre_tax * (rate1 + rate2). Reverse: pre_tax = post_tax / (1 + rate1 + rate2).
Source and editionArithmetic. No live rate lookup; user supplies state and local rates.
Free accessEach state's department of revenue publishes its current rate; user is responsible for the rate.
What governsEstimate. Verify before sending to your bookkeeper, banker, or CPA.
API field namespre_tax, rate1_pct, rate2_pct, tax, post_tax, combined_rate_pct
- Compounding additive (state + local rates summed before applying)U.S. state tax convention; some jurisdictions tax differently - verify locally