Property taxes are one of the largest carrying costs for any real estate investment — often the second-largest expense after mortgage interest. Yet many first-time investors treat the property tax figure as a fixed fact rather than a variable that can be managed, contested, and factored into acquisition pricing. Understanding how property taxes work, how assessments are made, and how they flow through your return calculations is essential to building an accurate financial model for any acquisition.

How Property Taxes Are Assessed and Calculated

Property taxes are calculated by multiplying the assessed value of a property by the local tax rate, which is expressed in mills — one mill equals $1 per $1,000 of assessed value. A property assessed at $400,000 in a jurisdiction with a tax rate of 20 mills carries an annual property tax bill of $8,000, or approximately $667 per month. The assessed value is determined by the local assessor's office and may or may not reflect current market value, depending on the jurisdiction and the frequency of reassessment cycles.

Some jurisdictions assess property at full market value, while others use a fixed percentage of market value — say, 70% or 80%. The effective tax rate you care about is the annual property tax bill divided by the current market value, not the nominal mill rate. A jurisdiction with a high nominal mill rate but a low assessment-to-market ratio may produce a lower effective tax bill than a jurisdiction with a low mill rate but full-market assessments.

Property Taxes in the NOI Calculation

Property taxes are an operating expense in the NOI calculation, which means they flow through to affect cap rate and cash flow. A $400,000 property with $8,000 in annual property taxes has a meaningfully different NOI than one purchased at the same price with $4,000 in annual taxes. When comparing properties, make sure you are using the actual current tax bill — not an estimate or the previous owner's figure, which may be outdated or incorrectly stated.

In many jurisdictions, property taxes are adjustable after a sale — the reassessment that follows a transfer of ownership means the new owner will receive a tax bill based on the new assessment, which may be higher than the seller's bill if the jurisdiction caps annual increases. Some jurisdictions, particularly in states like California with Proposition 13, limit annual assessment increases even upon transfer, which can create a significant discrepancy between market value and assessed value for long-held properties.

Contesting Your Assessment: When It Makes Sense

If you believe your property's assessed value is too high relative to market, you can typically file an appeal with the local assessor's office or a local board of revision. Successful appeals can reduce your tax bill meaningfully — a reduction from $8,000 to $6,000 in annual taxes saves $2,000 per year in carrying costs, which increases NOI by the same amount and adds roughly $25,000-$30,000 to the property's value at a typical 6.5-7.5% cap rate.

Appeals are most likely to succeed when you can document comparable sales that support a lower assessed value, when the assessor made factual errors in the property description (wrong square footage, wrong lot size, incorrect property condition), or when there is a clear discrepancy between the assessment and what similar properties are being assessed at after recent sales in the same submarket.

The Long-Term View: Tax Escalation and Planning

Property taxes tend to increase over time, even in jurisdictions with annual caps. When building a long-term pro forma for an acquisition, model a 2-3% annual increase in property taxes as a baseline assumption. In some markets, particularly rapidly appreciating urban markets, the annual increases can be more dramatic. A property purchased today with $8,000 in annual taxes could carry a $10,000 tax bill within five years — that $2,000 increase flows directly through to lower cash flow and should be reflected in your acquisition pricing accordingly.