Williamson County Property Tax & Sales Tax

Williamson County Tax Rates - At a Glance

Williamson County Current Tax Rates Summary

Tax Type	Rate	Notes
Property Tax (combined)	~1.68% of value	No single county rate - the sum of county, city, and school district. Representative nominal stack; typical effective rate runs about 1.61%.
Annual Vehicle (Car) Tax	None	Texas levies no annual value-based vehicle property tax
Sales Tax	8.25%	6.25% state + local portion capped at 2.0%; qualifying groceries exempt
Homestead Exemption	$140,000 school + 10% cap	Plus Williamson County local homestead (greater of $5,000 or 5%); over-65 adds $60,000 school + $125,000 county exemption
Due Date	January 31	Delinquent February 1; protest deadline May 15

Williamson County Property Tax

Williamson County property tax comes in two numbers that are easy to confuse. The county's own adopted rate is $0.413776 per $100 of value for the 2025 tax year - exact, from the Williamson County 2025 Tax Rates and Exemptions sheet (a $0.369447 general fund plus a $0.044329 farm-to-market/road fund). But that is only the county government's portion. Your actual bill is the sum of every overlapping taxing unit that covers your parcel: your school district, your city, and the county. Williamson County has no countywide hospital or college district on most bills - Austin Community College levies a tax only in annexed areas, not county-wide. Combined, the typical total effective rate in Williamson County is about 1.61% of market value - an estimate from Census ACS 2024 5-year data (median real estate taxes paid $7,205 divided by median home value $447,000). Because the mix of taxing units differs from parcel to parcel, there is no single "Williamson County rate" for a full bill; the figure below is a worked example.

How a typical Round Rock bill is built (taxing-unit stack)

School district City County

City of Round Rock / Round Rock ISD parcel - adopted rates per $100 (2025 tax year)

Taxing unit	Rate /$100	Type
Round Rock ISD	$0.8931	School
Williamson County	$0.413776	County
City of Round Rock	$0.3720	City
Nominal total	~$1.6789	~1.68%

Rates from the Williamson County 2025 Tax Rates and Exemptions sheet (county, City of Round Rock, Round Rock ISD). Round Rock ISD's rate is $0.8931 (M&O $0.7101 + I&S $0.1830). This example is for a City of Round Rock / Round Rock ISD parcel and excludes any MUD; your total depends on your city, school district, and special districts.

Two things stand out. First, the school district ($0.8931) is the single largest slice - on its own it is more than twice the entire Williamson County levy ($0.413776). Second, the nominal stacked rate of about $1.6789 per $100 (~1.68%) is a little higher than the ACS effective rate of about 1.61%. That gap is mostly exemptions: the school district, the biggest unit, only taxes value above the $140,000 homestead exemption, and the 10% appraisal cap holds down taxed values on long-held homesteads, so the rate people actually pay on market value is lower than simply adding the posted rates together. Note that because Round Rock ISD is one of the county's lower-rate school districts, this stack is on the low end for Williamson County.

Where your property-tax dollar goes

School district ~53% City ~22% County ~25%

On a typical City of Round Rock / Round Rock ISD parcel, the school district is about 53% of the bill (Round Rock ISD $0.8931 / $1.6789 nominal total). Williamson County is roughly 25% and the City of Round Rock about 22%. The county's share is larger here than in counties like Denton because Round Rock ISD's rate is comparatively low and the county's rate includes a farm-to-market/road fund. Percentages are rounded and use the nominal posted rates before any exemption.

Homestead exemption, the 10% cap, and key dates

If you own and occupy your home as your principal residence on January 1, you can claim a residence homestead exemption. For a Round Rock ISD parcel, that exemption removes $140,000 from the value the school district taxes for the 2025 tax year. If the owner is 65 or older, an additional $60,000 ISD exemption applies, plus a school-tax ceiling (freeze) that caps the school portion of the bill going forward. The school-district exemption lowers the school-district taxable value only - and Williamson County adds a local-option homestead exemption of the greater of $5,000 or 5% off the value the county taxes, plus an extra $125,000 county exemption for owners 65 or older or disabled. Check your parcel's full exemption list with the Williamson Central Appraisal District (WCAD).

Separately, the 10% homestead appraisal cap limits how much your homestead's appraised (taxed) value can rise to 10% per year, not counting new improvements. The cap applies to the appraised value used for your bill, not the market value the appraisal district sets, and it starts the year after you first qualify for the homestead exemption.

Worked example: on a $447,000 Round Rock ISD home with a homestead exemption, the school district taxes only $447,000 - $140,000 = $307,000, while the county and city tax up to the full value (less the county's local-option exemption). That single school-district difference is why the exemption matters most against the largest unit.

Key dates: Williamson County property tax is due January 31 and becomes delinquent February 1, when a 6% penalty plus 1% interest begins and increases monthly. To challenge your value, file a protest with the Williamson Central Appraisal District (WCAD) by May 15, or 30 days after your appraisal notice is mailed, whichever is later.

How to protest your appraisal

You can pursue an informal review with a WCAD appraiser, a formal Appraisal Review Board (ARB) hearing, or WCAD's online protest process. File and track everything at wcad.org. Some private firms offer to handle protests for a percentage of any tax savings; such firms exist and charge a contingency fee, but we do not cite any savings figure or success rate as fact - results vary by parcel and year.

Estimate your Williamson County property tax

Sources: the Williamson County Tax Office and the county's 2025 Tax Rates and Exemptions by Jurisdictions sheet (county, City of Round Rock, Round Rock ISD rates, 2025), the Williamson Central Appraisal District (exemptions, protest, dates), and Census ACS 2024 5-year estimates (typical effective rate).

Vehicle Taxes in Texas

Unlike many states, Texas does not levy an annual value-based property tax on cars or other vehicles. There is no yearly "car tax" bill in Williamson County. Instead, vehicle taxes in Texas work two ways:

• One-time motor-vehicle sales/use tax of 6.25% at purchase. For a private-party sale, the tax is charged on the greater of the actual sales price or 80% of the vehicle's Standard Presumptive Value (SPV). A vehicle received as a gift is taxed at a flat $10 instead.
• A flat annual registration fee (plus any local add-ons), which is a fixed fee, not a tax on the vehicle's value. In Williamson County you register and title through the Williamson County Tax Office.

So if you searched for a Texas car or vehicle sales tax, the answer is the one-time 6.25% charged when the vehicle is titled - there is no recurring vehicle property tax to budget for each year.

Williamson County Sales Tax

The combined sales tax rate in Round Rock is 8.25%. It is built from the state rate plus a local component - and Williamson County itself levies no county sales tax.

Round Rock (Williamson County) sales tax components

Component	Rate
Texas state rate	6.25%
City of Round Rock	2.00%
Williamson County	0.00%
Combined rate	8.25%

Texas law caps the total local portion at 2.0%. This is a shared ceiling, not additive past 2%: once the city and any special-purpose district rates add up to 2%, no further local rate can stack on top. That is why 8.25% is the maximum combined sales tax anywhere in Texas, including Williamson County. The City of Round Rock's 2% is made up of a 1% general city sales tax, 0.5% dedicated to property-tax reduction, and 0.5% for transportation and economic development; the local mix differs by city (Georgetown, Cedar Park, and others also reach 8.25% but split the local 2% differently). Qualifying groceries are exempt from sales tax.

Real Example: a $447,000 Round Rock Home

Here is how the numbers flow on a representative $447,000 City of Round Rock / Round Rock ISD home with a homestead exemption (owner under 65), using the school-district homestead only and excluding any MUD:

• Market value: $447,000.
• Homestead exemption: the school-district homestead exemption removes $140,000 from the Round Rock ISD taxable value, so the school district taxes $307,000. The city and county tax the full $447,000 in this simplified example (the county's own local-option exemption would lower its line slightly).
• Stacked total: school $307,000 × 0.8931% = ~$2,742; county $447,000 × 0.413776% = ~$1,850; city $447,000 × 0.372% = ~$1,663.
• Estimated annual bill: about $6,255 per year, before any MUD.
• Monthly equivalent: about $521 per month.
• Effective rate: about 1.40% of market value in this simplified example - lower than the county-wide ACS median effective rate of about 1.61%, because Round Rock ISD is one of the lower-rate school districts and this example applies the full homestead exemption. Many Williamson County parcels sit in higher-rate districts (Leander, Hutto, Georgetown) or a MUD, which lift the county-wide median.

Limitations:

• Your total varies by school district, city, and any special district covering your parcel; a MUD is common in fast-growing areas around Leander, Hutto, and Liberty Hill and is not included above.
• Local-option exemptions (the county's greater-of-$5,000-or-5% and $125,000 over-65, plus disability, disabled-veteran, and any city or school exemptions) vary by unit and can lower the bill further; this simplified example applies only the school-district homestead.
• New-construction homes are often taxed on land only in the first year, then jump once the structure is on the roll.
• A newly purchased home can reset toward your purchase price in year two, before your own homestead cap takes hold.
• This is an estimate, not a parcel-exact bill. The typical effective rate is a Census ACS estimate, not a guaranteed rate.