Portland property taxes explained: why the number on your bill has almost nothing to do with what you paid

shaan794

Sep 25

3 min read

Every Portland buyer eventually has the same confusing moment. They look up two houses on the same block, similar size, similar condition, similar price — and the property tax bills are thousands of dollars apart. Nothing about the houses explains it.

The explanation isn't about the houses. It's about 1990 and 1997.

Two numbers, not one

Oregon tracks two values for your property, and conflating them is the source of nearly all the confusion.

Real Market Value (RMV) is what the county thinks the property would sell for. This is the number that tracks reality.

Maximum Assessed Value (MAV) is a separate, artificial number created by Measure 50 in 1997. Properties were rolled back to a 1995–96 baseline, and from there MAV can grow by no more than 3% a year.

Your Assessed Value — the number your tax is actually calculated on — is the lower of those two. In a market that has appreciated faster than 3% a year for two decades, that's almost always MAV, and it's often far below what the house is worth.

Why your sale price doesn't reset anything

This is the part that surprises people coming from states like California-adjacent systems or from anywhere with acquisition-value assessment.

Buying the house does not reset its assessed value. The 3% ladder keeps climbing from where it already was, regardless of what you paid. Two identical houses can carry wildly different assessed values purely because of where each one happened to land in 1997 and what's been done to them since.

There are exceptions that do move MAV — new construction and significant remodeling add value outside the cap. That's worth knowing before you gut the kitchen: substantial improvement can raise the assessed value in a way that ordinary appreciation cannot.

Where Measure 5 comes in

Measure 5, passed in 1990, works on the other side of the equation. Instead of limiting value, it limits rates — expressed per $1,000 of real market value:

$5 per $1,000 of RMV for education
$10 per $1,000 of RMV for general government

When the combined taxes levied would push past those ceilings, the excess is "compressed" — reduced until the bill fits under the limit. Compression is why a newly approved local levy sometimes yields less revenue than voters expected: the money can't exceed the constitutional cap no matter what's on the ballot.

Because these limits are tied to RMV rather than assessed value, compression tends to bite hardest where market values have fallen or lagged, and to loosen where they've risen.

What this means when you're buying

Three practical moves.

Pull the actual tax record for the specific address before you write your offer, and put that number in your monthly budget — not a percentage-of-purchase-price estimate. In Multnomah, Washington and Clackamas counties this is public and takes two minutes.

Expect the bill to rise about 3% a year, not in proportion to your home's appreciation. That predictability is genuinely useful for long-range planning, and it's the one gift this system gives homeowners.

Factor renovation into the tax math. A major addition or a full remodel can add assessed value outside the 3% cap. Worth a conversation with the county assessor's office before you commit to a big project, not after.

Where this fits

Property tax is one line in the real cost of owning a Portland home, alongside insurance, maintenance and the systems that older stock eventually asks you to replace. Our guide to the true cost of Portland homeownership puts the whole picture together, and the Portland home buyer guide walks the budgeting sequence.

For the mechanics straight from a county assessor, this is a clear summary: Clackamas County, Measures 5 and 50.

Trying to work out what a specific house will actually cost you each month? Start a conversation.