How Oregon Property Tax Is Calculated: Rates by County Explained

When people relocate to Oregon from California, Texas, or most other states, they assume property taxes work the same way they're used to: a percentage applied to the purchase price. That assumption is wrong, and in Oregon it's expensive to get wrong.

Oregon uses a dual-value system set up by two constitutional amendments — Ballot Measure 5 (1990) and Ballot Measure 50 (1997) — that disconnects your tax bill from what you paid for the house. Two identical homes selling at the same price on the same block can have tax bills that differ by several thousand dollars per year, and the reason has nothing to do with current market value.

The Two Values on Every Oregon Property

Every Oregon property has two separate values on record with the county assessor:

Real Market Value (RMV): What the property would reasonably sell for on the open market as of January 1 of the assessment year. This is roughly equivalent to what appraisers and online tools estimate.

Maximum Assessed Value (MAV): A mathematically capped value established in 1997–98 at 90% of the property's 1995–96 RMV. After that baseline was set, Oregon law capped MAV growth at 3% per year, no matter how fast the market moves.

Taxable Assessed Value (AV): The value actually used to calculate your tax bill. It equals the lower of RMV or MAV. Because real estate values have risen far faster than 3% per year since 1997, nearly every Oregon home has an RMV much higher than its MAV — meaning the MAV is the operative number for tax calculation.

Why a Sale Doesn't Reset Oregon Property Taxes

This is the most important thing to understand: when you buy a property in Oregon, the sale does not trigger a reassessment. The property's MAV does not reset to your purchase price. The tax account simply continues forward with the historical MAV trajectory, regardless of what you paid.

This is the opposite of California's Proposition 13 system (which does reset taxes at purchase — you establish a new base year). It's also unlike most states where taxes are calculated as a straight percentage of assessed value tied to current market value.

In practical terms: an inner Portland Craftsman built in 1920, purchased in 2026 for $850,000, might have an MAV of $220,000 because its 1995–96 baseline was $240,000 (when that neighborhood was disinvested) and it has been growing at 3% per year since. Annual property taxes on that home could be around $3,500.

A newly constructed home in Hillsboro selling for $550,000 in 2026 was assessed at the time of completion using a post-1997 methodology, giving it an MAV close to its construction value. Annual property taxes on that home could be $6,000 or more.

Same price bracket. Opposite tax profiles.

The Changed Property Ratio (CPR): When Construction Triggers Reassessment

The 3% annual cap does not protect you forever. Specific "exception events" can bypass it and force an upward adjustment to the MAV:

• New construction or additions valued above $18,700 in a single year (or $46,200 cumulative over five years, with these thresholds indexed annually after 2024)
• Subdivision or partitioning of the land
• Property rezoning
• Discovery of "omitted property" — improvements like an unpermitted deck, finished basement, or ADU that the assessor didn't know about

When an exception event is triggered, the county assessor calculates the added RMV of the improvement and multiplies it by the Changed Property Ratio (CPR). The CPR equals the ratio of total assessed value to total real market value for similar properties in the county. If the CPR is 0.50 and you add improvements worth $100,000 in RMV, your MAV increases by $50,000.

This has a real-world implication for buyers: if you purchase a home and later discover unpermitted work done by the previous owner — a finished basement, a permitted ADU that wasn't on the tax rolls — the assessor can retroactively adjust the MAV when they discover the omission. Budget for this if you're buying an older home with visible renovation work.

Portland Property Tax Rates: Why Multnomah County Varies So Much

Multnomah County encompasses Portland, Gresham, and surrounding communities. The "property tax rate" you see quoted for Multnomah County is actually a composite of multiple tax authority rates layered on top of each other:

• City of Portland levy
• Multnomah County levy
• Portland Public Schools levy
• Metro regional government levy
• Multiple voter-approved bond measures (school construction, library operations, etc.)

These rates vary depending on which tax districts your specific property falls within. A home in Portland School District pays different rates than one in David Douglas School District, even if both are within Portland city limits.

The effective rate on a Multnomah County property typically falls in the range of 1.0% to 1.5% of assessed value — but because assessed value is significantly lower than real market value, the effective rate as a percentage of market value runs much lower, often 0.4% to 0.8%.

The only reliable number is the actual county tax certificate. Do not rely on Zillow, Redfin, or the listing sheet for property tax estimates. Before making an offer, ask your agent to pull the property's county assessment record and look at the current MAV and the assessed value used for the most recent tax bill. Your lender will use this to calculate your monthly escrow payment.

Measure 5 Rate Caps and Compression

Ballot Measure 5 set an additional safeguard: total property taxes cannot exceed $15.00 per $1,000 of Real Market Value — $5.00 for education taxes and $10.00 for general government taxes. Voter-approved general obligation bonds are exempt from this cap.

When the combined levy rates for all taxing authorities in a district exceed these caps, the county assessor applies "compression" — reducing rates proportionally until the total fits within the Measure 5 limits. Local option levies get compressed first (potentially to zero), then permanent rates.

Compression can mean that approved levies — including school funding measures voters approved — don't deliver the full amount intended. This is why some school districts in high-levy areas have had ongoing funding shortfalls even after successful ballot measures.

Property Tax Rates Across Oregon Counties

Because the MAV system means effective rates vary enormously by the age and history of the specific property, county-level "average" rates are rough guides at best. That said, county assessors publish consolidated rate summaries that give a baseline:

• Multnomah County (Portland): Effective rates on assessed value range from about $16–$20 per $1,000 AV across different tax code areas. On real market value, effective rates typically run 0.5%–1.1% depending on property history.
• Washington County (Hillsboro/Beaverton): Similar range to Multnomah, plus the only county in Oregon with a real estate transfer tax (0.1%, split between buyer and seller).
• Clackamas County (Lake Oswego, Happy Valley): Rates tend to run slightly lower than Multnomah due to fewer overlapping special district levies.
• Deschutes County (Bend): Generally lower than Portland metro, though newer construction comes with higher starting MAVs.
• Lane County (Eugene): Moderate rates; Eugene properties tend to have lower MAV-to-RMV ratios in established neighborhoods.
• Marion County (Salem): Lowest effective rates among major Oregon metro counties; median prices also lower.

The single-most useful action before making an offer on any Oregon property is to look up the parcel on the county assessor's website, find the current MAV and AV, and calculate: current tax bill ÷ current AV = current rate. Apply that rate to the same AV (which won't change unless an exception event occurs) to project your annual property tax liability.

The Oregon First-Time Home Buyer Guide includes a step-by-step property tax analysis worksheet that walks you through calculating your actual post-purchase tax bill using the MAV, the CPR, and county assessor data — so you're not relying on estimates that could be off by hundreds of dollars per month.

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