Trust · January 1, 2026

Methodology and sources

The calculator uses a fixed January 1, 2026 rate snapshot, not live address-specific rates. All 51 base, average-local, maximum-local and combined entries were compared with the cited January table on September 28, 2026. This confirms the dated transcription, not that a rate is current for a particular transaction. Explanatory notes were reviewed separately on September 28, 2026.

Primary sources

Tax Foundation, State and Local Sales Tax Rates, 2026 (as of January 1, 2026) (as of 2026-01-01)
Tax Foundation, State and Local Sales Tax Rates, 2025 (as of January 1, 2025) (as of 2025-01-01)

Tax Foundation compiles Sales Tax Clearinghouse ZIP data and state revenue publications into population-weighted local averages. We transcribed the January 1, 2026 table for the working calculator and kept January 1, 2025 combined figures for comparison. We did not license Sales Tax Clearinghouse itself.

What we store per state

Statewide base rate (percent)
Average local rate, 2026 and 2025
Average combined rate, 2026 and 2025
Maximum reported local add-on (2026)
A high-level sourcing label and a short note

Calculator math

Add tax: tax = round(amount × rate / 100),total = amount + tax. Reverse:preTax = round(total / (1 + rate / 100)),tax = total − preTax. Amounts are rounded half-up to cents before calculation, and monetary results are rounded half-up to cents using decimal arithmetic. Rates retain up to six decimal places. Amounts from $0 to $1,000,000,000 are supported. A custom local rate must be between 0 and 30% and is added to the base, even when a typical-local checkbox is selected.

What we leave out

ZIP+4 districts, product taxability, exemptions, holidays, marketplace facilitator splits, and bracket schedules. Those omissions are why the banner says the figures are approximate and not Avalara-grade.

Sourcing labels are high-level teaching summaries, not a legal matrix. The answer can depend on seller location, delivery, product and local law. Check the relevant revenue department for your transaction. Specific explanatory sources include Pennsylvania’s 2026 local-sales-tax guidance, Wisconsin’s county and city guidance, and South Dakota’s rate-reduction sunset notice.