Sources & Methodology

1. Our Editorial Mission for Sourcing

Every fact on a state or county page must be traceable back to a primary, authoritative source — most often the state revenue or taxation department, the county assessor’s office, or the relevant state code on the legislature’s site. If we can’t show where something came from, we don’t publish it. That principle is the foundation of every other process on this page.

Property tax in the US is uniquely fragmented: assessment is done at the county or municipal level, the legal framework is set by the state, and federal law (the Tax Cuts and Jobs Act SALT cap, for instance) overlays the picture. Each layer has different sources of truth — and confusing them is the most common error in non-specialist property tax content. Our hierarchy is built to keep them straight.

2. Six-Tier Source Hierarchy

Not all sources are equal. We rank them by authority and start at the top, moving down only when a higher-tier source doesn’t address the question:

3. Tier 1 — State Revenue and Taxation Authorities

For state-level law as administered — how the state defines assessed value, what ratios and caps apply, which exemptions are available statewide, and which forms taxpayers file — the state revenue, taxation or equalization authority is the highest authority. Names and structures vary state to state:

4. Tier 2 — County Assessors and Tax Collectors

Once you’re below the state framework, the address-specific assessment, parcel record, current bill and appeal procedure live with the county assessor’s office (or, in a handful of states, the township assessor) and the county tax collector / treasurer / sheriff. These are the offices that actually run the parcel lookup, send the bill and accept the payment.

Examples of Tier 2 offices we reference:

• Los Angeles County Assessor — assessor.lacounty.gov
• Cook County Assessor (Illinois) — cookcountyassessor.com
• Maricopa County Assessor (Arizona) — mcassessor.maricopa.gov
• Harris County Appraisal District (Texas) — hcad.org
• Miami-Dade County Property Appraiser — miamidade.gov property appraiser
• King County Assessor (Washington) — kingcounty.gov/depts/assessor
• San Diego County Assessor — sdarcc.gov
• Travis Central Appraisal District (Texas) — traviscad.org

State-level guidance about what an assessor does is not a substitute for the assessor’s own page on a specific parcel. A statewide ratio of 1.0 doesn’t tell you what the assessor put on your particular property — only the parcel record does that.

5. Tier 3 — State Codes and Legislatures

For the underlying statutory text — section numbers, definitions, exemption thresholds — we go to the official legislature or code revisor:

When we cite a statute, we include the full citation (e.g., Tex. Tax Code § 11.13, Cal. Rev. & Tax. Code § 218, Fla. Stat. § 196.031, N.Y. RPTL § 425) so a reader can verify against the legislature’s own page.

6. Tier 4 — IAAO and the Appraisal Foundation (USPAP)

For mass appraisal methodology, professional definitions and standards, we use:

• International Association of Assessing Officers (IAAO) — iaao.org — the standard-setting body for assessment professionals. IAAO standards on mass appraisal, ratio studies and personal property are referenced by most state DORs.
• The Appraisal Foundation — appraisalfoundation.org — publisher of the Uniform Standards of Professional Appraisal Practice (USPAP). Many states require USPAP compliance for fee appraisers and increasingly for mass appraisal.

7. Tier 5 — NCSL, Tax Foundation, Lincoln Institute, AARP

8. Tier 6 — Reputable US Press and Academic Research

For background context — a recent reform debate, a high-profile assessment lawsuit, a county that’s reorganizing its assessor’s office — we reference reputable US press (Wall Street Journal, New York Times, Washington Post, regional outlets) and academic research from US universities. Press and academic sources are never the sole source for a current millage rate, deadline or exemption threshold. Anything time-sensitive comes from Tier 1, Tier 2 or Tier 3.

9. URL Verification — Seven Steps to Stop Broken Links

1. Manual click-through. Every external link is clicked by an editor before publication. We confirm the page loads, the destination matches the topic, and the URL is the canonical one.
2. Domain check. Government sources should be on a .gov, .us or state-specific government domain. State revenue authority URLs are confirmed against the state government index.
3. Content match. The destination page must actually be the page we describe. A homestead exemption link that lands on a generic “Forms” page doesn’t pass — we link to the actual exemption page.
4. HTTPS preference. Where the source publishes both, we link to HTTPS.
5. Quarterly re-verification. Every external link on every page is re-checked at least quarterly.
6. Reader-reported breakage. Broken links reported by readers are fixed within seven business days.
7. No Google Search fallbacks. If we can’t verify a county’s specific page, we don’t link to a Google Search results page as a substitute. We mark the section with a [VERIFY] placeholder or omit it.

10. Fact-Checking Workflow

Every state and county page goes through this workflow before publication:

1. Drafter pulls facts from Tier 1 and Tier 2 sources — the state revenue authority for the framework, the county assessor and tax collector for parcel-specific procedure. Each fact gets a source note.
2. Editor reads the source pages in full, including any “important,” “service alert” or update banners that often hold the most current information.
3. Statutory text is verified against the legislature or code revisor (Tier 3) wherever a section is cited.
4. URLs are tested live, not assumed.
5. Critical numbers are confirmed against the authority’s current page — millage rates, exemption thresholds, appeal deadlines, and assessment caps in particular get extra attention because they change with each fiscal year.
6. Second editor reviews the page end-to-end before it goes live.
7. “Last reviewed” date is set to the publication date.

11. The Two-Source Cross-Reference Rule

Time-sensitive facts — an appeal deadline, a homestead exemption threshold, a school district millage rate — must be confirmed by two independent sources before they go on a page. Acceptable combinations include:

• The state revenue authority’s published guidance and the county assessor’s own application of it
• The state code (Tier 3) and the state revenue authority’s administrative guidance
• The county assessor and the county tax collector for items both publish (such as billing dates and delinquency thresholds)

If two sources disagree, we go with the more authoritative one for the specific question — usually the assessor for parcel-level facts, the state revenue authority for statewide rules, and the legislature for statutory text — and flag the conflict to the editorial team for resolution.

12. Update Cycles — Aligned to the US Property Tax Calendar

13. Citation Standards

• External links open in a new tab with rel="noopener" for security
• Affiliate links use rel="nofollow noopener sponsored" per FTC endorsement guidance
• Primary citations link directly to the state revenue authority page, county assessor page, or statute in question
• Statutory references use the standard short-form citation (e.g., Tex. Tax Code § 11.13, Cal. Rev. & Tax. Code § 218) and link to the legislature’s official version
• Form numbers are cited with both the form number and the issuing authority (e.g., Form 50-114 issued by the Texas Comptroller, Form BOE-266 issued by the California State Board of Equalization, Form DR-501 issued by the Florida Department of Revenue)
• Last-reviewed dates appear on every state and county page so readers can judge freshness

14. What We Don’t Use

• Property-tax-protest consultant marketing pages. We don’t cite a consultant’s blog as authority for a county’s appeal procedure. The county assessor’s appeal page is the authority.
• Anonymous tax blogs. Even when factually accurate, anonymous content can’t be verified or held to account.
• Wikipedia as a sole source. Useful for orientation, never as the sole basis for a fact on a state or county page.
• AI-generated content from other sites. We don’t republish or paraphrase content we can’t trace to a primary source.
• Wayback Machine snapshots in place of current pages. Archived snapshots are useful historical reference but never a substitute for the assessor’s or revenue authority’s current page.
• Social media posts from individuals or unofficial accounts, regardless of follower count.
• Out-of-state guidance applied across states. Texas appraisal rules don’t apply automatically in Florida; California Prop 13 caps don’t apply in any other state. We treat each state’s framework separately and never paste rules across borders.
• Real estate listings as source for assessed value. Assessed value and market value are different concepts; Zillow estimates and listing prices are not Tier 1 sources for assessed value.

15. Reader Contributions and Corrections

Readers are an important part of our verification system. If you spot a discrepancy — your county assessor’s page says one thing and ours says another, or a state-level fact has changed since our last review — please email info@propertytaxusa.org with subject line “Correction” and the URL of the page in question. The full corrections workflow is on the Editorial Policy page.

Reader-reported corrections are our priority queue. Corrections from readers who can include the authority’s link supporting the change are processed fastest — typically within 48 hours.

16. Audit Trail and Openness

Where a journalist, researcher or property-tax professional needs to verify how we sourced a particular page, we make our editorial notes available on request. Email us with the URL of the page and the specific factual claim you want to trace, and we’ll respond within seven business days with the underlying source links and editorial notes. Transparency is a feature, not a cost.

Our broader stance on independence, advertising disclosure and conflict-of-interest management is on the Editorial Policy. The general framework that disclaims any official-government identity is on the Disclaimer.