How are assessed values calculated for property tax purposes

I was playing around on the OC gov's tax site athttp://ocgov.com/octaxmaprecently. I noticed that two homes in my neighborhood that sold recently for a higher price then what we had paid for our homes more than 10 years ago had lower assessed value then our home. The square footage for the other 2 homes is about 100 sq feet less than ours.

I was under the impression that the assessed value was impacted by the sale price. Is that not the case?

Also, one of the homes is still not showing up as sold on Redfin. However Zillow is showing it as sold. The other home is showing up as sold both on Redfin and Zillow. I never saw a for-sale sign on either of these homes. The owners did move out of both homes and new owners (renters?) did move in. Wonder if this was a family-to-family sale that doesn't show up on the tax records.

It takes a while for county records to update. It?s probably just a lag in time. Look in a couple of months for the supplemental bill, which is essentially a true up to the sales price.

It doesn't matter what homes sold in your area as the tax assessor will use your sales prices to determine your property tax.  In future years, they'll use closing comps to determine if the property tax value should increase or decrease.  The County assesses property taxes from July through Sept and they mail out the tax bills around late Sept.  As Qwerty mentioned, you'll most likely get a supplemental tax bill from the delta between the previous owner's basis and your purchase price through the end of June 30th.

Another possibility could be that the new owner is over age 55 and transferred over his base value from his old property to the new property.  Look at Prop 60/90.