The mortgage estimate looked fine. The purchase price made sense next to the comps. Then the first full winter tax bill arrived, and the number was nowhere near what anyone budgeted for. This happens often enough across Oakland County that real estate agents have a name for the moment: the uncapping surprise. It is not a mistake anyone made. It is Michigan's property tax system doing exactly what it was built to do, and it lands hardest on buyers who assumed the seller's tax bill was a preview of their own.
Here is the thesis worth sitting with before you write an offer in Troy: the property tax figure on any listing tells you what the seller has been paying, and almost nothing about what you will pay. The gap between those two numbers can be the size of a car payment, and it has nothing to do with the home's condition, size, or finishes. It has to do with how long the seller owned the house and how much Troy has appreciated since they bought it.
The Mechanism Behind the Gap
Michigan's Proposal A, passed in 1994, caps how fast a home's taxable value can climb each year while the same owner holds title. For 2026, the state set that cap at 2.7 percent. A homeowner who bought in Troy a decade ago has watched their taxable value crawl upward by a few percentage points a year, even as the home's actual market value climbed much faster. That gap between taxable value and true market value is the seller's protection, and it disappears the moment the deed changes hands.
The state explains the trigger plainly: a transfer of ownership causes the taxable value to uncap in the calendar year following the transfer. The buyer does not inherit the seller's capped number. The taxable value resets to the State Equalized Value, roughly half of the assessor's estimate of market value, and a fresh cap begins building from there. Whatever the seller's tax bill said on the listing sheet, it describes their ownership history, not your future liability.
What Troy's Own Numbers Show
The City of Troy publishes its own worked example on the millage rates page, and it is worth sitting with because it shows exactly how the formula bites. Using a taxable value of $150,550 against Troy's combined millage of 30.6705 mills, the estimated yearly tax comes to $4,617.44. That is straightforward arithmetic. What it does not show is which taxable value gets plugged into that formula, the seller's long-held, capped number or the buyer's freshly uncapped one. Those can be two very different starting points for the exact same house.
Troy's citywide numbers back this up. Tax data aggregator Ownwell puts Troy's median effective property tax rate at 1.28 percent, well above the national median of 1.02 percent and Michigan's statewide median of 1.05 percent, with a median annual bill of $4,380 against a national median of $2,400. Troy taxes are not low to begin with. Layer an uncapping event on top of that baseline and the jump for a new buyer gets real fast.
Why Two Nearly Identical Houses Can Carry Very Different Bills
Here is where the story gets more interesting than a simple tax lesson. Troy is not one tax rate. It is several, stitched together by school district and assessment district boundaries that do not follow the neighborhood lines buyers actually think in. Ownwell's ZIP-level breakdown shows the spread directly:
| ZIP Code | Median Effective Rate | Estimated Annual Bill |
|---|---|---|
| 48083 | 1.24% | ~$3,402 |
| 48098 | 1.32% | ~$5,542 |
That is a difference of more than $2,100 a year between two ZIP codes inside the same city, and Ownwell attributes it to how school district boundaries and local assessment districts are drawn across Oakland County. A buyer comparing two Troy listings at the same price, in different school districts, is not just choosing between floor plans. They are choosing between meaningfully different annual carrying costs, and the seller's current tax bill on either listing tells them almost nothing about which one is the better deal once uncapping resets both numbers to market.
Stack that district variance on top of ownership tenure and the range widens further. A house held by the same family for fifteen or twenty years in an appreciating Oakland County market can carry a taxable value that sits far below its State Equalized Value. When that ownership finally turns over, the new taxable value snaps up to match SEV in one move, and increases of 40 to 60 percent over what the seller had been paying are common in Oakland County transactions when the gap has had decades to widen. That is not a Troy-specific quirk. It is the same Proposal A mechanism playing out anywhere long ownership meets rising values, and Troy has plenty of both.
The Paperwork Timeline That Actually Determines the Number
The uncapping is not automatic in the sense of happening the moment you sign at closing. It runs on its own filing schedule, and missing a step costs real money.
Within 45 days of closing. Buyers of Troy property must file the Property Transfer Affidavit, Form L-4025, within 45 days of the transfer date. This is the form that notifies the assessor a sale happened and sets the uncapping in motion for the following tax year. Skipping it does not stop the reset. It just adds a penalty.
By June 1 for the summer bill. If the home will be your primary residence, file Form 2368 with the Troy City Assessor by June 1 to claim the Principal Residence Exemption. It removes up to 18 mills of school operating tax from the bill. Miss the date and you are paying non-homestead rates on top of an already uncapped taxable value, which compounds the surprise.
If you want to contest the new assessment. Michigan's Board of Review sessions convene each March, and in 2026 appeal meetings began on Monday, March 9, with individual municipalities sometimes shifting the exact day within that week. This is the venue for challenging a State Equalized Value you believe overstates market value, and it is the only path before the taxable value locks in for the year.
One more wrinkle worth knowing if you are selling to a family member rather than an unrelated buyer: certain transfers between closely related parties, including transfers to trusts under specific conditions and transfers between spouses, may not trigger uncapping at all. That exception does not apply to a typical arm's length sale, but it matters for anyone structuring a transfer within the family.
What This Means If You're Buying in Troy
Treat the tax line on any Troy listing as a data point about the seller, not a line item for your own budget. Before you get attached to a monthly payment estimate, ask what the current State Equalized Value is and run the math against Troy's published millage rate for the school district that specific address sits in. If you are choosing between two homes in different ZIP codes, price the tax gap into your comparison the same way you would price a finished basement or an updated kitchen. A $2,100 annual swing between 48083 and 48098 is real money over the life of a mortgage, and it will not show up if you only compare list prices.
What This Means If You're Selling in Troy
Your own tax bill is not the problem here, but your buyer's underwriting can become one if nobody corrects the assumption early. Lenders often build estimated escrow off the number currently on file, which is your capped figure, not the buyer's future uncapped one. If that gap is wide because you have owned the home a long time, a buyer's lender can flag an escrow shortfall during underwriting that stalls the closing timeline or spooks a buyer who feels blindsided. Getting ahead of that conversation, sharing the SEV and a realistic post-sale estimate up front, keeps the deal moving instead of reopening it two weeks before closing.
A Few Questions We Hear Often
Does the tax increase happen immediately at closing? No. The reset takes effect the calendar year following the transfer, so the first full bill at the new, uncapped rate typically arrives the year after you close.
Is there any way to avoid uncapping on a normal purchase? Not on an arm's length sale between unrelated parties. The exemptions are narrow and mostly cover family transfers, certain trusts, and transfers between spouses.
Can a new owner appeal the assessment after uncapping? Yes, through the March Board of Review sessions and, if needed, the Michigan Tax Tribunal afterward. It will not undo the uncapping itself, but it can correct an SEV that overstates true market value.
If you are weighing a Troy purchase or getting ready to list, the tax math is one more place where a second look before you write an offer or set a price saves a lot of friction later. Kim Nagy and the team have been walking Metro Detroit buyers and sellers through exactly this kind of local detail for over three decades. Contact Us when you are ready to talk through what a specific Troy address will actually cost you to own, not just what it costs to buy.
