Property taxes in Pennsylvania are calculated by multiplying a property’s assessed value by the combined millage rates set independently by three local taxing bodies: the county, the municipality (borough, township, or city), and the school district. The state itself collects no property tax. All 67 counties, roughly 2,560 municipalities, and 500 school districts set their own rates and bill separately, which is why two similar houses a few miles apart can carry very different tax bills.
The core formula looks like this:
Tax Owed = (Assessed Value − Homestead Exclusion) × (Millage Rate ÷ 1,000)
You run it once for each of the three taxing bodies and add the results. Everything else in the system, from base year assessments to the Common Level Ratio to Act 1 rate caps, is really about how the two numbers in that formula get set.
Assessed Value Is Not Market Value
The first number you need is your assessed value, which the county assessor’s office assigns. Most Pennsylvania counties operate under a base year system authorized by 72 P.S. § 5020-402. Rather than reappraising every property each year, the county freezes assessed values based on market conditions from a single historical date. In some counties that base year was set decades ago, so the figure on your bill can look nothing like what your home would sell for today.
Once set, your assessed value only changes under limited circumstances: a countywide reassessment, which counties conduct infrequently because they are expensive, or a physical change to the property itself, such as adding a second story, building a detached garage, or demolishing a structure. Absent one of those triggers, the base year figure carries forward year after year.
Pennsylvania’s constitution contains a Uniformity Clause that bars counties from picking out individual properties for reassessment, a practice known as spot reassessment. A county cannot single out recently sold homes for reappraisal while leaving neighbors at stale figures. Any reassessment has to be countywide or tied to a physical change on the parcel.
Interim Assessments on New Construction
If you finish new construction or a major addition after January 1, you may not wait until the next full tax year for a bill. Under 24 P.S. § 6-677.1, school districts and municipalities can request an interim assessment on new construction and collect a proportional tax for the remainder of the fiscal year, provided the taxing body has an ordinance authorizing the practice.
Millage Rates and What a Mill Means
The second number in the formula is the millage rate. One mill equals one dollar of tax for every $1,000 of assessed value. If the combined rate across all three taxing bodies is 50 mills and your assessed value is $100,000, the bill before any exclusion is $5,000.
Each of the three taxing bodies sets its own rate through an annual budget process. School district taxes typically make up the largest share of the total, often more than the county and municipal portions combined. School board rates are subject to limits under Act 1 of 2006. For the 2026–2027 school year, the base index restricting how much a district can raise its rate without voter approval is 3.5%.1Pennsylvania Department of Education. SSAct1 BaseIndexHistory 2026-27 Districts with greater financial need can receive a slightly adjusted index, but going above the allowed cap requires a referendum. Your specific rates appear on your annual tax bill and on your local government’s website.
Walking Through the Calculation
Say your home is assessed at $150,000 and you receive a $10,000 homestead exclusion on the school portion. Your local rates are 5 mills (county), 3 mills (municipality), and 25 mills (school district):
- County: $150,000 × 0.005 = $750
- Municipality: $150,000 × 0.003 = $450
- School district: ($150,000 − $10,000) × 0.025 = $3,500
- Total annual tax: $4,700
Two things are worth noticing. First, the homestead exclusion reduces only the school portion. County and municipal taxes apply to the full assessed value. Second, because each taxing body sets its own rate, changes in one do not automatically move the others. Your county rate can hold flat while your school district raises its rate within the Act 1 cap, and your total bill still goes up.
The Homestead and Farmstead Exclusion
The Taxpayer Relief Act (Act 1 of 2006) created the homestead and farmstead exclusion, which subtracts a fixed dollar amount from your assessed value before the school millage rate is applied.2Pennsylvania General Assembly. Act of Jun. 27, 2006, Special Session 1, P.L. 1873, No. 1 – Taxpayer Relief Act The dollar amount varies by district because it is funded from each district’s share of state gaming revenue plus any locally designated earned income tax revenue.
For the 2025–2026 school year, $1.025 billion in state gaming revenue is available statewide to fund these exclusions.3Pennsylvania Department of Education. Property Tax Reduction Allocations At that funding level, qualifying homestead properties are guaranteed between 12.5% and 50% property tax relief. Your actual exclusion amount is printed on your school tax bill.
To qualify, you must own and occupy the property as your primary residence and file an application with your county assessment office by March 1. Once approved, the exclusion carries forward until you sell, move out, or otherwise stop using the home as your primary residence. When a sale is recorded, the exclusion is typically removed automatically effective January 1 of the following year. If you convert the home to a rental or second property without selling, you are responsible for notifying the assessor.
The Common Level Ratio: Not on Your Bill
Because base year assessments grow stale over time, the State Tax Equalization Board publishes a Common Level Ratio for each county every year, certified before July 1 and effective for the following twelve months.4PA Department of Community & Economic Development. State Tax Equalization Board (STEB)/Tax Equalization Division (TED) The CLR is where most people get confused, so it is worth being clear: the ratio is used in the assessment appeal process only.5Pennsylvania Department of Community and Economic Development (DCED). Common Level Ratio 2024 It does not appear on your regular tax bill and does not automatically adjust your assessed value.
Where it matters is during an appeal. If you file with the county’s Board of Assessment Appeals and prove a current fair market value, the board applies the CLR to that figure to produce a number comparable to base year assessments across the county. A CLR of 0.60 and demonstrated market value of $200,000 would translate to an appropriate assessed value of $120,000. That mechanism keeps an appealing homeowner from being penalized for offering current market evidence when everyone else’s assessment is frozen at a much older figure.
Payment Timing, Discounts, and Penalties
Bills go out in two waves. County and municipal bills usually arrive around March 1, and school district bills around July 1. Under the Local Tax Collection Law (Act 394 of 1945), every taxing district must offer a discount of at least 2% to taxpayers who pay within two months of the bill date, and unpaid taxes incur a penalty of up to 10% after four months.6Pennsylvania General Assembly. Act of May 25, 1945, P.L. 1050, No. 394 – Section 10 The 2% is a floor, so your district may offer a larger early-payment discount. The 10% is a ceiling, so the actual penalty could be lower where you live. Between the discount cutoff and the penalty date, you pay the face amount.
School districts in the second, third, and fourth class are also required to let homestead- and farmstead-eligible homeowners pay their school property taxes in installments rather than a single lump sum. Since 2012, that installment option has extended to qualifying small business owners as well.7Pennsylvania General Assembly. Section 1502 – Installment Payment of School Real Property Taxes Your school tax collector can confirm the specific schedule your district uses.
Put the pieces together and the calculation is not complicated, even if the system that produces the two inputs is. Find your assessed value on any recent bill or your county assessor’s website. Find the current millage rate for each of the three taxing bodies. Subtract your homestead exclusion from the assessed value before applying the school district rate, and leave it in place for county and municipal calculations. Add the three results. That is your annual property tax in Pennsylvania.