Your Oregon property tax statement carries two values for the house. Real market value is what the county thinks it would sell for. Assessed value is the number the tax is computed on, and for most houses it's a lot lower. That second number is why the bill goes up every year, and why a neighbor in the same floor plan can pay hundreds less than you do.
The rule comes from two ballot measures. Measure 5 in 1990 capped the tax rates. Measure 50 in 1997 set each property's assessed value at its 1995 level minus 10%, then let it grow no more than 3% a year from there. Your tax is the assessed value times the local rate, so as long as the market value stays above the assessed value, the bill climbs about 3% a year no matter what the market does. Flat year, up 3%. Down year, still up 3%, until the market value falls below the assessed value, which for most Oregon homes would take a very large drop.
Selling the house doesn't reset it. In California the assessed value jumps to the purchase price when a home changes hands. In Oregon it keeps rolling along at 3% from wherever it was, so two identical houses bought decades apart can carry very different tax bills. What does move it is new construction. Add a bedroom or finish a basement and the county adds that value to the assessed number, and it stays there.
So most appeals go nowhere. People see a real market value on the statement that's higher than what the house would sell for and file. But if the assessed value is the lower of the two, and it usually is, knocking the market value down changes nothing unless you can get it below the assessed value. The appeal is a real tool in the year after a big local downturn, and a wasted afternoon otherwise. Petitions go to the county's property value appeals board, with a December 31 deadline.
The bill itself arrives in October and is due November 15. Pay the whole thing by then and the county takes 3% off. Pay two-thirds and it's 2%. Pay in three installments through May and there's no discount at all.
At the end of the day the bill is assessed value times the rate, so the number to watch is the difference between the two values on the statement. If your market value is $520,000 and your assessed value is $310,000, the county has a long runway of 3% increases ahead of it, and no dip in the market is going to touch your bill. Budget for the 3% the same way you'd budget for any other bill that's guaranteed to grow, which means a line in the non-monthly bills plan rather than a surprise every October.