We get this question a lot.
Nobody wants to get an increase in their assessed value after filing for a reduction. People want to know the risks involved in filing a property tax appeal.
Assuming you have nothing to hide, such as added square footage that was not permitted by the County Building Department, there is very little risk in filing a property tax appeal.
First of all, in California the assessor is prohibited from assessing your property above the “factored base value.” The factored base value is generally your purchase price, or value at the date of completion of construction, increased or decreased annually by inflation factors, but not more than 2% per year.
My advice is to always file an appeal, because it can be withdrawn, and you have no risk of an increase, and at least an opportunity for a decrease. And my experience is that property reassessed with new base year values is generally not appraised by the assessor with the same care that will occur after an appeal. In other words, further scrupulous attention results in a different value, and usually it is less. So go for it.