Look up and compare sourced U.S. state income, estate, and inheritance tax reference data with field-level citations and verification receipts. Estimate state income tax when required inputs are substantiated, compare jurisdictions, and inspect dataset versions and coverage. Missing, uncited, unverified, pending-final, and not-applicable values remain distinct and are never silently treated as zero. All tools are read-only and require no account or API key. This is reference data, not tax or legal advice.