Property taxes are the one line in a rental budget you cannot negotiate, cannot shop, and cannot manage down. A seller will move on price and a broker will find you another carrier. The county sets your bill on a value you do not control, and collects whether the unit is rented or vacant.
That would be tolerable if the number were small and predictable. It is neither. Effective rates run from around half a percent of value or lower in the calmest states to north of two percent in the worst, a swing of hundreds of dollars a month on the same house. And the tax figure printed on the listing usually belongs to the current owner. In a lot of counties it resets the day you close. That is how a clean 1% rule deal becomes a break-even before you collect a rent check.
the mechanics
The math is boring; the trap hides inside it. The county multiplies its own rate by the assessed value of the parcel, and one twelfth of that annual bill is your monthly tax line. Both numbers are the county's. Assessed value is its opinion of the property, which can sit far above or far below what you paid, and the rate is a millage set by the taxing districts, while an assessment ratio decides what share of market value that millage lands on, so millage alone tells you nothing. What lets you compare markets is the effective rate: the bill as a percentage of what the property is really worth. Where the assessment tracks market value, a 100% ratio being common, the two rates match. Where it is stale or capped, the effective rate on the owner's current bill sits well below the rate the county will apply to you.
Where that number lands in the stack matters as much as its size. Property tax is an operating expense, so it comes out above the line: rent minus operating expenses gives you net operating income, and debt service comes out of NOI after that. The tax line hits NOI, cap rate, DSCR, and cash flow at once, and no financing structure moves it. The rest of that stack is in the guide to rental property operating expenses. Taxes are the line with the widest variance and the least room to manage.
Two more traits are worth naming. Taxes never retire: pay the loan off and the county still bills you every year, which is why a free-and-clear property is never actually free. And they move without asking. Millage gets voted up, assessments get revisited on the county's own schedule, and a bill you underwrote at closing can be meaningfully higher three years in. Model a rising line, not a flat one.
the spread that matters
Treat rates as known ranges rather than a table you memorized. The calmest states land around half a percent of value or lower. The highest run north of two percent. Everything else falls in between, and the number you actually need is a county figure, sometimes a school-district figure, never a state average. Two houses a mile apart on opposite sides of a line can carry very different bills on identical value.
Put that on a $150,000 house. At half a percent, the tax is about $63 a month. At 1.2%, it is $150. At 2.5%, it is about $313. Nothing about the building changed and the rent did not move. The gap between the ends is roughly $250 a month, $3,000 a year, on a property that might have cleared $200 a month in the first place. That is why a cheap price in a high-tax county routinely underperforms a pricier house somewhere calmer. The ranking of the best markets to invest in 2026 treats tax drag as a number that separates metros.
the reassessment trap
Here is the one that catches investors who did everything else right. The tax figure on the listing, and in the public record behind it, is the current owner's bill, computed on an assessment that may be thirty years old. Many counties reassess on transfer: your sale becomes the new evidence of value and the assessment resets toward what you paid. Several states also cap how fast an owner's assessed value can climb, which makes the gap between a long-held assessment and a fresh one enormous. The cap protected the seller for twenty years. It starts over from your price.
Work it through. You buy at $150,000 in a county whose rate is 2.5%. The seller has held it a long time on a $60,000 assessed value, so the listing shows $1,500 a year, or $125 a month. That is the number you underwrote. After closing, the assessment resets toward your purchase price: $150,000 at 2.5% is $3,750 a year, about $313 a month. Nearly $200 a month appeared out of nowhere, permanently. Notice what the listing implies, though: a $1,500 bill on a $150,000 house reads as a 1.0% effective rate. That rate is real, it is just the seller's, and copying it into your model is the entire mistake.
Now run that through the deal. Rent is $1,500 on a $150,000 purchase, the textbook 1% property. Finance 75% at around 7.5% on a 30-year term and principal and interest come to roughly $787 a month. Add $100 of insurance and set aside 20% of rent, $300, for vacancy, maintenance, and reserves. Underwritten on the listing's tax bill, cash flow is $188 a month. Underwritten on the bill you will actually receive, it is zero. Not thin, not tight: dead even, every month, on a property that looked like the textbook deal.
- principal & interest$787
- insurance$100
- reserves 20%$300
- taxes$125
- cash flow$188
- principal & interest$787
- insurance$100
- reserves 20%$300
- taxes$313
It moves financing at the same time. PITIA goes from about $1,012 to $1,200, so DSCR on $1,500 of rent falls from roughly 1.48 to 1.25. Still fundable at most lenders, but closer to the line, and a lender who reruns taxes at the post-sale number can quote a different pricing tier. Run the ratio at the reassessed figure before you write the offer. The DSCR calculator takes the tax number directly, so feed it the one you expect to pay.
The worked numbers above are illustrative. These are not: three listings from the catalog right now, underwritten with taxes and insurance in the payment stack instead of rent minus mortgage.
homestead vs investor rates
There is a quieter version of the same problem: in plenty of places an investor pays more than an owner-occupant on the identical property. Homestead exemptions remove a slice of assessed value for people who live in the house, and that slice comes off the roll when you are not one of them. Caps on annual increases are frequently tied to owner occupancy, so non-homestead property gets a looser cap or none. Some jurisdictions go further and classify non-owner-occupied property separately, at a higher assessment ratio.
None of this appears on a listing. It appears the year after you close, when the exemption drops off the roll and the bill rises on a property you already own. The rules vary by state and county, so this is a call-the-assessor item, and anything with real money attached deserves a tax professional licensed in that state. Three questions cover most of it: does this parcel reassess on sale, does the current bill carry a homestead exemption, and what is the rate for non-owner-occupied property here.
the underwriting rule
One sentence: underwrite property taxes as the county's own rate applied to what you are about to pay, never as the tax bill on the listing. If the county does not reassess on transfer, you were conservatively wrong and the deal gets better after closing. If it does, you were right and you did not buy a break-even by accident. Being wrong that way costs nothing. Being wrong the other way costs you the cash flow the deal was built on.
Getting the rate right is a ten-minute job on the assessor site, and it turns on one detail: derive the rate from the county's own number, not from market value. Divide the parcel's current annual bill by its taxable value, meaning assessed value less exemptions, which is the figure the county actually multiplies. Then apply that rate to your purchase price times the assessment ratio the assessor publishes, 100% in a lot of counties. On the example: $1,500 over the $60,000 taxable value is 2.5%, and 2.5% of a $150,000 purchase at a 100% ratio is $3,750 a year, the $313 a month you will really pay. Divide the same bill by the $150,000 the house is worth and you get 1.0%, straight back into the trap.
- Pull the parcel record: assessed value, taxable value, annual bill, exemptions.
- From the bill: annual bill ÷ taxable value is the county rate. Apply it to purchase price × assessment ratio.
- Or from the assessor: millage × assessment ratio is the effective rate. Apply that one to purchase price alone.
- Cross-check with a comparable that sold recently: its first post-sale bill ÷ its sale price.
- No owner-occupant exemption in your number, and never the existing assessment.
- Confirm whether the county reassesses on transfer, and budget for millage drift across the hold.
None of this is exotic. It is one division and one multiplication, done on the right numbers instead of the convenient ones. The rental property analyzer puts taxes and insurance where they belong, above the line, so the cash flow on screen is the cash flow after the county takes its cut. Investors who get hurt in cheap markets almost never got the rent wrong. They took the tax line off a listing page and never asked the assessor what happens next.