Williamson County, TX — Property Tax Underwriting Guide
Texas · Annual market review
What this means for multifamily underwriting
Williamson County (Round Rock, Cedar Park, Georgetown) is a high-growth Austin suburb. Appraised values have risen sharply; ARB protest is a standard line-item in the operating budget.
Transaction type breakdown
Texas appraisal districts appraise property annually as of January 1 using mass-appraisal methods. A transaction may provide relevant market evidence, but ownership transfer does not mechanically reset the assessment to, or toward, purchase price.
Refinance does not change appraised value.
Ownership transfer does not mechanically reset the assessment to, or toward, purchase price; annual January 1 appraisal continues under the district's mass-appraisal process.
Tax appeal information
20.0 mill (2.0% effective) is a mid-county estimate for Williamson.
Guide review
County guidance last reviewed: June 15, 2026
Tax-rate scope: County-level underwriting placeholder; not a parcel-specific tax rate.
Official sources: Williamson CAD
Annual-market model is well established; aggregate millage is a placeholder.
Parclio estimates are underwriting guidance, not legal or tax advice. Always verify millage rates, the seller's assessed value, and appeal deadlines with the county assessor or local counsel before relying on these numbers for a credit decision.
Run a tax reset estimate for Williamson County
Use Parclio's estimator to model the post-closing tax bill, NOI impact, DSCR change, and underwriting memo language for your next Williamson County deal.