You’ve found a house in Round Rock you like. The listing shows last year’s property taxes, and the number looks manageable. Then your lender sends a loan estimate, and the tax line is hundreds of dollars a month higher than you expected. Which one is right?

Here’s the short version: the number on the listing belongs to the seller.

What you’ll pay depends on three things. The first is the value the appraisal district puts on the home. The second is the combined tax rate of every local government that taxes that address. The third is the exemptions you personally qualify for and file. The seller’s bill reflects the seller’s exemptions and, often, years of capped increases. None of that comes with the house.

I’m Andrew Clements. I’m a licensed realtor and general contractor working across the greater Austin area, including Round Rock, Georgetown, Hutto and the rest of Williamson County. Before my clients make an offer, I estimate what their property taxes will actually be, because it changes the monthly payment more than most people expect. Below is how property taxes work in Williamson County, how to estimate your own, and how to keep the bill as low as the law allows.

Who Sets Your Property Taxes in Williamson County

Three separate players are involved, and it helps to know who does what.

The Williamson Central Appraisal District, usually called WCAD, decides what your home is worth for tax purposes as of January 1 each year. WCAD also handles homestead exemption applications and value protests. It’s based in Georgetown, and you can reach it at 512-930-3787 or wcad.org.
Taxing units each set their own tax rate. For most homeowners that means Williamson County, your school district, and your city if you live inside city limits. Depending on the address, you may also see a community college district, an emergency services district, or a municipal utility district (MUD).
The Williamson County Tax Assessor-Collector mails the bill and collects the money on behalf of those taxing units.

The easiest way to see every unit that taxes a specific property is the county’s rate database at WilliamsonPropertyTaxes.org. Type in the address and you’ll see each line that makes up the bill.

Looking at the county database matters because Texas has no state property tax and no state income tax. Local schools, cities, and counties are funded largely through property taxes, so the bill tends to run higher here than in many other states. The rate you pay depends on which of those local units your address falls inside.

How Your Tax Bill Is Calculated

The math is simpler than it looks. For each taxing unit:

(appraised value − exemptions) ÷ 100 × that unit’s tax rate

Then you add up the results for every unit on your bill. Rates are written as dollars per $100 of value, which is why you divide by 100.

One detail catches people off guard: exemptions apply unit by unit. The big $140,000 homestead exemption only reduces the school district portion of your bill. It doesn’t lower what you owe the county or the city.

Let’s run a real example using 2025 rates. Every taxing unit sets a new rate each fall, so your numbers will be different in 2026 and beyond, but the method stays the same.

Say you buy a $450,000 home inside Round Rock city limits and Round Rock ISD.

Williamson County’s 2025 rate was $0.413776 per $100, according to the county’s budget announcement. That comes to about $1,862.
Round Rock ISD’s 2025 rate was $0.8931 per $100, adopted by the school board in September 2025. Without a homestead exemption, that’s about $4,019. With the $140,000 exemption, your taxable school value drops to $310,000 and the school tax falls to about $2,769.
The City of Round Rock’s 2025 rate was $0.372 per $100, per the city’s tax rate ordinance. That’s $1,674.

Add it up and you get about $7,555 a year, or roughly $630 a month, without a homestead exemption. With it, the bill drops to about $6,305 a year, or roughly $525 a month. The school exemption alone is worth about $1,250 a year on this house.

Your address may carry more lines than these three, such as a MUD or a community college district, and some units offer their own local exemptions. Look up your full list on WilliamsonPropertyTaxes.org before you build a budget.

For a sense of how rates move, Williamson County adopted its 2026-27 budget on September 1, 2026 at the no-new-revenue rate, which is the rate that brings in roughly the same revenue from the same properties as the year before. Community Impact reported that works out to about $28 less on the county portion for the average homeowner. Other units on your bill make their own decisions each year.

The Listing’s Tax Bill Is Not Your Tax Bill

This is the part I most want buyers to understand, because it’s where the surprises come from. It shows up in three common situations.

Buying a resale home

Texas limits how much the taxable value of a homestead can rise each year to 10%, plus the value of any new improvements. That limit belongs to the owner who has the homestead exemption. When the house sells, the cap and the seller’s exemptions end. Your first full bill is based on the home’s market value and the exemptions you file for yourself.

If the seller has owned the home for ten years in a market where values have climbed, their taxable value may sit well below market value. Homeowners 65 and older can also have a school tax ceiling that freezes their school taxes. A buyer inherits none of it. That’s why a long-time owner’s tax bill can look dramatically lower than what you’ll pay.

Buying new construction

WCAD values property as of January 1. If your home was a bare lot or a half-built frame on that date, the first bill may reflect only the land or the partial structure. Your lender sets up escrow based on that small number, and your payment looks great for a year.

Then the next January comes, the finished home gets its full value, and you receive an escrow shortage notice with a higher monthly payment on top of it. The fix is easy if you plan ahead: ask your lender to set escrow using the estimated value of the completed home, not the lot.

Remodeling or adding on

Here’s where my experience as a contractor comes in. The 10% cap doesn’t cover new improvements. If you add a room, finish out space, or build a pool, WCAD can add the value of that work to your appraisal on top of the capped amount. I’m not saying skip the project. I’m saying go in knowing it will likely show up on your tax bill. If you’re thinking about updates before selling, my post on renovation before listing covers which projects tend to pay off.

The takeaway: before you make an offer, estimate the taxes from the purchase price, not the tax history. I do this for every client, because it’s one of the biggest variables in whether a home fits your budget. My post on how much you need to make to buy a home in Round Rock shows how taxes fit into the full monthly payment.

Exemptions That Lower Your Bill

Exemptions are the single biggest lever you control. Here are the ones most Williamson County homeowners should know about, based on the Texas Comptroller’s exemption guide.

The general residence homestead exemption takes $140,000 off your home’s value for school district taxes. It used to be $100,000. Texas voters raised it by approving Proposition 13 on November 4, 2025, with 79.41% voting yes, and it applies starting with the 2025 tax year.
Homeowners who are 65 or older, or who have a disability, get an additional $60,000 off school district value. Homeowners 65 and older also qualify for a school tax ceiling, which caps the school portion of their bill.
Cities, counties, and some other districts can offer a local option homestead exemption of up to 20% of your home’s value, with a minimum of $5,000. Not every unit offers one, so check your WCAD record to see which apply at your address.
Disabled veterans and certain surviving spouses have their own exemptions. The Comptroller’s guide lists the requirements.

How and when to file

You file your homestead exemption with WCAD using its online exemption application. The general deadline is April 30.

Here’s the good news for buyers. You don’t have to wait until next year. Under Texas law, if you buy your home after January 1 and the previous owner didn’t receive the same exemption that year, you can claim the homestead exemption for the part of the year you own it. My advice is to file as soon as you’ve closed and moved in. It takes a few minutes, and it’s money you don’t want to leave on the table.

How to Protest Your Appraised Value

If WCAD’s value on your home looks too high, you have the right to protest it. A lot of homeowners never do, and some of them are overpaying.

WCAD starts mailing notices of appraised value around April 1. The protest deadline is May 15, or 30 days after your notice was delivered if that’s later. You can file through WCAD’s online protest portal.

Here’s how to put together a protest that holds up.

Request WCAD’s evidence packet. Texas law lets you see the information the appraisal district plans to use at your hearing, and WCAD has a request form on its site. Read it so you know which sales they’re comparing your home to.
Pull your own comparable sales. Look for homes similar to yours in size, age, and location that sold for less than your appraised value around January 1. A realtor can help with this, and if you’d like a second opinion on your home’s value, you can request a free home valuation.
Document condition problems. This is where most people leave money behind. If your home has foundation movement, an aging roof, or an HVAC system on its last legs, take photos and get written repair estimates. A contractor’s written bid for a roof replacement is real evidence that your house is worth less than a comparable home with a new roof.
Try the informal review first. Many protests are settled in a conversation with a WCAD appraiser before they ever reach a formal hearing. If you can’t agree, your case goes to the Appraisal Review Board.

Key Dates for Williamson County Homeowners

Put these on your calendar. They come from WCAD’s property tax deadline calendar and the Williamson County Tax Assessor-Collector.

January 1 is the date WCAD uses to set your home’s value and decide which exemptions you qualify for.
Around April 1, WCAD begins mailing notices of appraised value for homes.
April 30 is the general deadline to file exemption applications.
May 15 is the protest deadline, or 30 days after your notice arrives if that’s later.
By late September, each taxing unit adopts its tax rate for the year.
Around October 1, tax bills go out.
January 31 is the payment deadline. Taxes are delinquent on February 1, and penalties and interest begin.

If you’re 65 or older or have a disability and your home has a homestead exemption, Williamson County offers a quarter-payment plan with installments due January 31, March 31, May 31, and July 31.

If you escrow your taxes through your mortgage, your lender pays the bill. It’s still worth checking your WCAD notice every spring, because the value on that notice drives next year’s escrow.

Know Your Real Number Before You Buy

Property taxes in Williamson County aren’t a mystery once you know the pieces: a value set on January 1, a stack of local rates, and the exemptions you file for. The number on a listing tells you what the seller paid. It doesn’t tell you what you’ll pay.

Before you make an offer anywhere in Williamson County, I’ll run the tax numbers on that exact address so the payment you plan for is the payment you get. And if you’re already in your home and your appraisal jumped, I’m happy to look at that too. Reach out and let’s talk it through.

Frequently Asked Questions

When are Williamson County property taxes due?

Tax bills go out around October 1 and are due by January 31 of the following year. Unpaid taxes become delinquent on February 1, when penalties and interest start. Homeowners 65 and older or with a disability who have a homestead exemption can use the county’s quarter-payment plan.

Can I get a homestead exemption the year I buy my house?

Yes, as long as the previous owner didn’t receive the same exemption for that year, according to the Texas Comptroller. File with WCAD as soon as the home becomes your primary residence.

Do property taxes go up when a house sells in Texas?

The tax rate doesn’t change because of a sale, but the seller’s exemptions and 10% homestead cap don’t carry over to you. Your bill is based on the home’s market value minus the exemptions you qualify for, which is often more than the seller was paying.