Before you spend a minute on an appeal, it's worth knowing whether you actually have a case. Here's a plain, honest way to tell whether your Philadelphia assessment is too high — and when the gap is big enough to act on.
In Philadelphia, your property tax is driven by a single figure: the market value the Office of Property Assessment (OPA) assigns to your home. That value is multiplied by a combined City and School District rate to produce your bill. So the question "is my home over-assessed?" really means one thing: is OPA's market value higher than what my home would actually sell for today? If it is, you're paying tax on money you don't have.
OPA doesn't send an appraiser to walk through every house. It uses mass appraisal — a statistical model applied across hundreds of thousands of parcels at once. That approach is efficient, but it's blunt. It can miss a block that hasn't appreciated as fast as its neighbors, a home in below-average condition, or a plain factual error in the property record. Each of those can push your value above where it belongs.
You don't need software to get a first read. Here's the core comparison any homeowner can do in an afternoon:
The honest part of this test is that it cuts both ways. Plenty of homeowners run it and discover their assessment is actually fair — and that's genuinely useful to learn, because it saves a wasted weekend. The goal isn't to talk yourself into an appeal; it's to find out whether the evidence is on your side. Getting the comparison right is the hard part, which is why it's worth reading how to find comparable sales that hold up before you lean on any single number.
A few patterns show up again and again in genuinely over-assessed properties:
Over-assessment isn't about your home being expensive. It's about the number on the notice being higher than the number a buyer would actually pay.
Not every gap is worth chasing. Mass appraisal will never be perfect to the dollar, and a difference of a few percent is usually inside the normal margin. The gaps worth acting on are the ones you can document: a cluster of comparable sales clearly below your value, or a hard record error you can point to. Because Philadelphia tax recurs every year, even a modest reduction compounds — a fair value you win once keeps paying you back on every future bill, which is a big part of why the math often favors filing when the evidence is real. If you're weighing whether your particular gap clears the bar, our use-case walkthrough on deciding whether to appeal lays out the trade-off in more detail.
It also helps to understand exactly how that value becomes a dollar figure, because it tells you what a reduction is actually worth. Our page on how Philadelphia property taxes are calculated walks through the rate applied to your assessed value, so you can translate any gap you find into real annual savings.
The manual test works — it's just slow and easy to get wrong, because picking truly comparable sales takes judgment. TaxAssessmentIQ pulls your live OPA record, finds real comparable sales automatically, and shows you the gap between your assessed value and what the comps support. It tells you plainly whether an appeal looks worth filing, and if it does, it builds a Board-ready packet you can sign and send yourself. No lawyer, no consultant taking a cut of your savings — just the research done for you, so you can decide with evidence instead of a hunch. If the numbers say your assessment is fair, it tells you that too.
It means the market value the Office of Property Assessment assigned to your home is higher than what your home would realistically sell for. Because your tax bill is calculated directly from that market value, an inflated figure means you are paying more than your fair share.
There is no official threshold, but a small gap of a few percent is usually within the normal noise of mass appraisal and may not be worth the effort. A gap of ten percent or more, backed by genuinely comparable sales, is the kind of difference that tends to justify filing.
Yes. If the OPA record lists the wrong square footage, an extra unit you do not have, or a lot size that is too large, that error may have inflated your value on its own. Correcting a factual error is one of the cleanest grounds for a reduction.
No. Reviewing your own OPA record and looking at nearby sales is free, and TaxAssessmentIQ lets you run the comparison and see whether a gap exists at no cost before you decide anything.
Then filing an appeal is unlikely to help, and it is better to know that up front than to spend a weekend building a case that the evidence does not support. An honest check saves you from chasing a reduction that is not there.
TaxAssessmentIQ gives you a free, honest verdict from the City's own recorded sales — just enter your address, no sign-up and no account. If your home looks over-assessed, you can get a ready-to-file appeal packet for a flat, one-time price, backed by a money-back guarantee. If it isn't worth filing, we tell you that too — for free, before you pay anything.
Free in public beta — no charge to check your assessment or build your packet.