Observed arrival · 2026-09-09
Withholdwell turns payroll tax calculations into an API call
A US payroll tax API for gross-to-net pay, bonuses, self-employment tax, and overtime calculations.
Field notes
The API accepts payroll inputs including annual gross pay, state, filing status, pretax retirement percentage, and pay frequency, then returns annual and per-period figures with a line-item receipt. Each result carries a tax-year marker and data_version hash intended to identify the exact tables behind the calculation. Coverage is broken into statutory, none, estimate, and unset categories; the page specifically flags Indiana county tax omissions and declines to model AR, DC, and VT where sources conflict.
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