Data Sources & Methodology
Transparency about where our statistics come from and how we verify accuracy.
Our Data Philosophy
Every statistic on TaxCase Review is sourced from verifiable, authoritative data. We believe taxpayers deserve accurate information to make informed decisions. This page documents our primary data sources, update frequencies, and verification processes.
Primary Data Sources
Internal Revenue Service (IRS)
Official government data on tax collection and enforcement
IRS Data Book
Annual publication with comprehensive collection statistics, lien filings, levy actions, and Offer in Compromise acceptance rates.
irs.gov/statisticsIRS Collection Activity Reports
Quarterly reports on installment agreements, Currently Not Collectible status, and collection case resolutions.
Notice of Federal Tax Lien Filings
Public records of federal tax liens filed with county recorders across all 50 states. We aggregate these to create county-level statistics.
IRS Internal Revenue Manual (IRM)
Official procedural guidance for IRS employees, used to verify our descriptions of IRS processes and policies.
irs.gov/irmCounty Recorder Offices
Public records of federal tax lien filings
Federal tax liens are public records filed with county recorder offices. We aggregate data from county records across our coverage states to provide local statistics:
Legal & Regulatory Sources
Authoritative legal references
Internal Revenue Code (IRC)
Title 26 of the U.S. Code — the primary statutory basis for all tax procedures we describe.
Treasury Regulations
Official interpretations of the IRC issued by the Treasury Department.
U.S. Tax Court Decisions
Published opinions that establish precedent for tax resolution procedures.
Taxpayer Advocate Service Reports
Annual reports to Congress identifying taxpayer issues and IRS performance metrics.
taxpayeradvocate.irs.govIndustry & Economic Data
Context for industry-specific content
Bureau of Labor Statistics (BLS)
Employment data by industry and geography for our industry-specific content.
U.S. Census Bureau
Population, income, and business statistics for state and county analysis.
Federal Reserve Economic Data (FRED)
Economic indicators that provide context for tax collection trends.
Data Update Frequency
| Data Type | Update Frequency | Last Updated |
|---|---|---|
| IRS Data Book Statistics | Annually | January 2026 |
| County Lien Filings | Monthly | June 2026 |
| OIC Acceptance Rates | Annually | January 2026 |
| IRS Procedure Descriptions | As policies change | Ongoing |
| Industry Statistics | Quarterly | Q2 2026 |
Data Verification Process
Source Documentation
Every statistic is documented with its original source URL, publication date, and the specific table or page reference where the data was found.
Cross-Reference Check
When possible, we cross-reference data against multiple sources. For example, county lien totals are checked against both county records and IRS state-level aggregates.
Expert Review
A tax professional reviews data interpretations to ensure we're presenting statistics in proper context without misleading implications.
Freshness Monitoring
We track when source data is updated and refresh our statistics accordingly. Content using outdated data is flagged for immediate update.
Data Limitations
Important Disclaimers
- Lag time: IRS data is typically 6-18 months behind current activity. County data is more current (1-3 months lag).
- Estimates: Some county-level statistics are estimates based on state-level data and population/income ratios when direct data is unavailable.
- Rounding: We round large numbers for readability (e.g., "45,000+" rather than "45,237") unless precision is important for context.
- No individual advice: Aggregate statistics cannot predict individual case outcomes. Your situation may differ significantly from averages.
Questions About Our Data?
If you have questions about a specific statistic or want to report a data error, please contact our research team.
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