References & official tax resources
Official IRS, state revenue, VAT, and GST portals we use to fact-check calculators and guides—open in a new tab and confirm current rates before you file or remit.
Trusted sources we cite and recommend
We link to official tax agencies, standards bodies, and established references — not random blogs — so you can verify rates and rules yourself.
US federal tax guidance
- IRS — Small business & self-employed Federal tax resources, forms, and educational material for businesses and individuals.
- IRS Publication 334 — Tax guide for small business Overview of federal tax obligations relevant to small business recordkeeping.
- IRS — State government websites Directory linking to each state revenue or taxation department.
State & local sales tax
- Streamlined Sales Tax Governing Board Member states, rate lookup tools, and registration guidance for multistate sellers.
- Federation of Tax Administrators Links to state tax agencies and policy resources across the United States.
- California CDTFA — Sales & use tax Example of a state department page with rates, publications, and filing info.
Accounting & bookkeeping
- AICPA — Financial reporting resources Professional context for US GAAP concepts cited in business expense guides.
- FASB — Accounting standards Authoritative source for US GAAP standards referenced in educational content.
- SBA — Manage your business finances Practical guidance on separating business expenses and keeping records.
VAT, GST & global tax
External links open in a new tab. We are not affiliated with these agencies. Always confirm current rates on official sites before filing or remitting tax.