Technically they can go down. Property taxes declined in California back in 2009-2010 when the bubble popped. Then valuations went up a few years later by a lot (more than 2%) when buying homes came back in style. Los Angeles county(?) wanted to capture the full valuation increase, arguing that the 3-4% increase would only bring it back to where it was before the recession. Taxes are only supposed to go up by 2% annually by law. A judge ruled in favor of the full increase. The other weird prop tax story was some mid west county/city making a valuation mistake, something like $10,000,000 million instead of $100,000 on a parcel. The mistake was found after the county had already factored in the mistake into the budget; no one questioned the big increase in expected tax payments. Rather than cut spending the municipality just raised everyone's property taxes.