Allegheny County still uses 2012 as the base year for property assessments. Some Mt. Lebanon homes have had their values changed through appeals since then, but the 2012 base underlies every bill. On August 17, 2026, Allegheny County Common Pleas Judge Kenneth G. Valasek ordered the county to replace those base values with a countywide reassessment. If you're buying in Mt. Lebanon this fall, the tax figure on the listing sheet probably won't be the one you pay for as long as you own the house.
Most coverage asks whether taxes will go up. For Mt. Lebanon as a whole, the rules mostly answer no. The better question for a buyer is whether this particular house will end up carrying a bigger share of the bill than it does now. The 2012 values are being replaced, but the total amount of tax Mt. Lebanon collects mostly isn't. The burden gets redivided.
The Clock, in Order
The order sets deadlines, and as of October 15 it has someone in charge of holding the county to them.
- Within six months of the August 17 order: the county has to hire a reassessment contractor, as PublicSource reported.
- October 15, 2026: Administrative Judge Alan Hertzberg appointed Judge Mary McGinley to oversee the reassessment. The county and the plaintiff couldn't agree on an outside expert, according to the Pittsburgh Post-Gazette.
- By July 1, 2027: work has to materially begin.
- Before June 30, 2032: the reassessment has to be finished.
How often the county reassesses after that is still being worked out. The county's own announcement described five-year cycles. In August, the county's Government Review Commission recommended every four years, WESA reported. A County Council bill calling for three-year cycles was still in committee at that point.
So if you close in 2026 and stay five years or longer, your tax bill will very likely be recalculated while you own the house.
Why the Total Mostly Stays Put
Pennsylvania's anti-windfall rules require taxing bodies to cut their millage after a reassessment. The Government Review Commission's draft report on property assessment and taxation puts it plainly:
"Reassessment changes how the tax base is divided among property owners; it does not automatically give the county permission to collect more money."
A Mt. Lebanon address pays three taxing bodies, and each one follows a different rule.
| Taxing body | 2026 millage | Rule after reassessment |
|---|---|---|
| Municipality of Mt. Lebanon | 4.50 | Must first set a rate that brings in no more than the prior year. A separate vote can allow up to 10% more, under the Consolidated County Assessment Law, §8823 |
| Mt. Lebanon School District | 32.033 | Exempt from §8823. The first-year increase is limited by the Act 1 index under Taxpayer Relief Act §327 |
| Allegheny County | 6.43 | County Code §5-809.03 caps reassessment revenue from existing property at 100% of the prior year. State law and the county charter would allow up to 105% with a separate vote, per the commission's report |
Those three rates add up to 42.963 mills, or about $42.96 for every $1,000 of taxable assessed value before any exemptions, according to the Municipality of Mt. Lebanon's tax page. New construction and improvements are counted separately, because they're real growth in the tax base and not a higher value put on property that was already there.
Mt. Lebanon Already Ran This Experiment Once
The last reassessment gives a useful preview. The Allegheny County Controller's records from the 2012-to-2013 changeover show Mt. Lebanon School District's certified assessed value rising 25%, from about $2.175 billion to about $2.708 billion. Over the same change, the district's millage fell 17%, from 27.13 to 22.61. The municipality did the same thing. Its assessed base rose 27% and its millage dropped from 5.43 to 4.51.
The rates since then show what happened next. The municipal rate is 4.50 mills today, almost exactly where the rollback left it. The school rate climbed from 22.61 back to 32.033. That climb came from ordinary budget votes over the years, not from the reassessment. The latest one was this year. In June, PublicSource reported that the district was considering raising its rate from 30.95 to 32.033 mills to close a $4.2 million deficit, and that district leaders said property tax appeals had significantly cut into revenue.
Here's what that means for a buyer. A reassessment year resets the rate. The budget votes that follow decide where it goes from there.
The Math That Decides Your Bill
The rollback works on totals, but bills are paid one house at a time. Here's a made-up example with round numbers. Say the school district's existing tax base comes back 50% higher after reassessment. To bring in the same revenue, the 32.033 mill rate would have to fall to about 21.36 mills.
| Hypothetical home | Value change vs. 2012 base | School tax bill after rollback |
|---|---|---|
| House A | Up 50%, same as the base | About the same |
| House B | Up 80% | About 20% higher |
| House C | Up 20% | About 20% lower |
The 50% figure is invented to show how the math works. It isn't a forecast for Mt. Lebanon. The pattern holds at any number, though, and the commission's report describes it the same way: if total value doubles, the rate falls by roughly half, and individual bills move depending on whether a property gained more or less than the rest.
A Mt. Lebanon homeowner actually runs this comparison twice:
- School and municipal taxes: your house compared with the rest of Mt. Lebanon. A renovated house on a street that has seen strong sales gets measured against neighbors who may have gained less.
- County taxes: Mt. Lebanon as a whole compared with the rest of Allegheny County. If Mt. Lebanon's values have grown faster than the county average since 2012, its share of the county's 6.43 mills grows. If they've grown slower, its share shrinks.
For scale, Allegheny County's common level ratio for tax year 2027 is 49.3%. That's the figure applied to current market value in appeals heard starting September 2026. It means assessments across the county now average about half of what properties sell for. That gives a rough sense of how large the countywide reset could be, though it can't tell you how any single Mt. Lebanon house will come out.
Two Houses With the Same Assessment Aren't the Same Purchase
Under the current system, some properties' assessments have already been reset through appeals, at market value times the common level ratio, and others haven't. Mt. Lebanon has been part of that. In 2014, Mt. Lebanon Magazine reported that the municipality decided to appeal 156 homes sold in 2013. It chose homes based on how far the sale price exceeded the assessment. That's history, and it doesn't describe how any taxing body in Mt. Lebanon selects appeals today.
Appeal law has also shifted recently. On May 19, 2026, the Pennsylvania Supreme Court ruled in Downingtown Area School District v. Chester County Board of Assessment Appeals that a neutral dollar threshold for choosing which properties to appeal doesn't, by itself, violate the state constitution's uniformity clause. The court specifically left open whether targeting only recently sold properties is allowed.
For a buyer, the useful question about any house is how its current assessment was set. A home that's still at its 2012 value and a home that was reassessed after a recent sale can show similar tax bills today and come out of the reassessment very differently.
The Protection Program Comes With Conditions
Allegheny County passed a Longtime Owner-Occupant program in February 2026. It doesn't take effect until the county's tax rolls are first revised after a countywide reassessment. According to the ordinance:
- It generally requires living in the same primary residence for 10 straight years, with household income at or below 125% of area median income.
- It limits the first increase to 35% over the lowest county bill of the prior five years. After that, the bill can rise 7% a year until it reaches the full amount, or until the owner has received relief for 10 years.
- It applies to county taxes only, and participants give up the county homestead exclusion.
At 2026 rates, the county's 6.43 mills are less than a sixth of a Mt. Lebanon homeowner's total millage. The school and municipal portions aren't covered by the program. Someone buying this year also wouldn't reach the 10-year occupancy requirement until 2036.
A Few Direct Questions
Will my Mt. Lebanon taxes go up because of the reassessment? Whether yours go up depends on how your property's new value compares with the rest of each taxing body's base. Each body also keeps the option of a separate rate vote within the limits shown above. The rollback stops a body from collecting a windfall just because values went up. It doesn't freeze any one person's bill.
When would new values show up on a bill? The order requires work to begin by July 1, 2027, and finish before June 30, 2032. No exact date has been set for when new values reach bills.
Can I still appeal my current assessment? The appeal window for tax year 2027 ran July 1 through September 1, 2026, and used the 49.3% common level ratio. Details for future years are on the county's Board of Property Assessment Appeals and Review page.
This post is general information, not legal, tax or financial advice. Check how these rules apply to a specific property with a tax attorney, an accountant or the county assessment office.
If you're comparing Mt. Lebanon houses and want to know how each one's assessment was set and where it might stand after the reassessment, Nate Nieland can go through the property records with you before you make an offer. Book an appointment and bring the addresses.
