Primary sources
- Reciprocity and withholding: the exemption certificates themselves, plus state revenue department guidance. Where a secondary source and the form disagreed, the form won.
- Unemployment insurance: the US Department of Labor Employment and Training Administration's Significant Provisions of State UI Laws, Effective January 2026 for wage bases, new employer rates and rate ranges, cross-checked against state agency pages where they differed.
- Localization test: the DOL Unemployment Insurance Program Letter guidance on localization of work.
- Experience-rating method: the DOL Comparison of State UI Laws, financing chapter. This is the most recent published edition and is noted as such wherever it appears.
What is not confirmed
Fields that could not be verified from a state's own publication are stored as empty and rendered as "not confirmed" rather than filled in. That is deliberate: a wrong number presented confidently is worse than an acknowledged gap. Notable cases include several de minimis thresholds that appear only in practitioner compilations, and a handful of indexed dollar amounts that change annually.
Compilation notes
Built 2026-08-13 for a US multi-state payroll withholding tool. Reciprocity agreements, nonresident exemption certificates, and de minimis withholding thresholds were verified against state Department of Revenue / Taxation .gov sources wherever possible; Tax Foundation (2026) and COST were used only as corroboration and are flagged in per-field notes where a .gov confirmation could not be obtained. Rates are 2026 tax-year top marginal (graduated) or single (flat) rates and EXCLUDE local income taxes. IMPORTANT: reciprocity is directional in several cases -- Arizona's arrangement (CA/IN/OR/VA) is a one-way exemption from ARIZONA withholding and is NOT mutual, and DC's is a broad statutory bar on taxing nonresidents rather than a bilateral agreement. Reciprocity agreements generally cover STATE income tax only and do NOT exempt an employee from LOCAL income taxes in the work state (notably Indiana county LIT, Ohio municipal tax, Pennsylvania EIT/Philadelphia wage tax, Kentucky occupational license taxes, Maryland county tax). The key 'conveniencOfEmployer' is intentionally spelled that way to match the consuming code. Any field that could not be verified is set to null with an explanatory note -- values were not guessed. Verify against the current-year state employer withholding guide before relying on this for production payroll. All URLs in this file were HTTP-checked on 2026-08-13; a few state sites (dor.ms.gov, otr.cfo.dc.gov, mass.gov, revenue.nh.gov, des.az.gov, dol.ks.gov, ui.nv.gov, revenue.mt.gov, dws.arkansas.gov) block automated requests and return 403 or refuse the connection to scripted clients while resolving normally in a browser.
Reciprocity and withholding corpus
dam.assets.ohio.gov · pa.gov · tax.illinois.gov · tax.illinois.gov · in.gov · michigan.gov · revenue.wi.gov · revenue.wi.gov · revenue.state.mn.us · tax.nd.gov · revenue.ky.gov · revenue.iowa.gov · tax.virginia.gov · tax.wv.gov · marylandcomptroller.gov · otr.cfo.dc.gov · azdor.gov · revenue.mt.gov · nj.gov · nj.gov · revenue.nebraska.gov · tax.ny.gov · portal.ct.gov · files.hawaii.gov · maine.gov · dor.sc.gov · tax.utah.gov · taxfoundation.org · taxfoundation.org · cost.org · taxfoundation.org
Unemployment insurance corpus
oui.doleta.gov · oui.doleta.gov · oui.doleta.gov · oui.doleta.gov · payroll.org · symmetry.com · taxnews.ey.com
Currency
Data compiled 2026-08-13 for the 2026 tax year. Reciprocal agreements, thresholds and wage bases all change; re-verify against the linked state source before relying on any determination for a filing position.