What MUD taxes really cost in Williamson County (2025 rates)

Williamson County has 75 municipal utility districts with a 2025 tax rate. Here is what they add to a home's tax bill, with real examples and a free estimator.

Two homes at the same price, a few miles apart in Williamson County, can carry tax bills that differ by thousands of dollars a year. The biggest single reason is usually a three-letter acronym buyers rarely notice until closing: MUD.

Want your own number? Use our free Williamson County property tax estimator. Pick the city, school district and MUD and it builds the bill line by line.

What a MUD is

A municipal utility district is a special taxing district, usually created when a new community is built. It borrows money to pay for water, sewer and drainage infrastructure, then repays that debt with its own property tax on every home inside its boundary. The tax is added on top of the county, school district and (if the home is inside city limits) city taxes.

How many there are, and what they charge

According to the Texas Comptroller’s 2025 rate data, 75 MUDs in Williamson County levy a tax. Rates are set per $100 of taxable value:

• The lowest MUD rate is $0.09 per $100.
• The median is $0.682 per $100.
• 31 MUDs charge $0.75 or more, and five charge the maximum of $1.00 per $100.

For scale, Williamson County’s own 2025 rate is about $0.41 per $100. A MUD at the median rate costs more than the county does.

What that means on a $600,000 home

Here is the same $600,000 home, owner-occupied with the homestead exemption, in a few common setups. Figures use 2025 adopted rates:

That last row is roughly $6,000 a year more than the same home with no MUD, or about $500 a month. On a mortgage payment, that is the difference between two very different price ranges.

Why the homestead exemption matters

If the home will be your primary residence, Texas school districts must exempt $140,000 of its value from school taxes. Counties that charge a farm-to-market or flood control tax, as Williamson does, exempt another $3,000 from that portion. MUD and city taxes apply to the full value unless the district adopts its own optional exemption. File for the homestead exemption with the appraisal district after you close.

PIDs are a separate line item

A public improvement district (PID) also funds community infrastructure, but through an annual assessment rather than a tax rate, so it does not show up in state tax rate data. If a home is in a PID, the assessment appears in the seller or builder disclosures and on the tax bill. Ask for the PID amount before you write an offer, and add it to the MUD and HOA when you compare homes.

Questions to ask before you buy

1. Is the property in a MUD, PID, or both? What are the current rates or assessments?
2. Is it inside city limits, or covered by an emergency services district?
3. What are the HOA dues, and what do they cover?
4. For new construction: what was the home appraised at last January 1? A home finished mid-year can carry a much smaller first bill than it will in year two.

You can confirm the taxing units for any address on the Williamson Central Appraisal District property search.

The bottom line

MUDs are not a reason to avoid a community. They are how much of Williamson County’s newer housing gets built, and the infrastructure they fund is real. They are a reason to compare homes on full monthly cost (price, tax, MUD, PID and HOA together) rather than price alone.

Run your numbers with the property tax estimator, or set up a home search for the areas you are considering and we will flag the MUD, PID and HOA on every home you like.

Estimates use 2025 adopted rates from the Texas Comptroller (data version January 28, 2026) and include the state-mandated homestead exemptions only. 2026 rates are adopted in the fall. This article is general information, not tax advice.