South Valley Spotlight - Santa Clara County
Fast tax math for Morgan Hill, Gilroy, and San Martin buyers, heirs, and over-55 movers.
Use this before you make an offer, accept an inherited home, move a parent into a family property, or try to carry an old Prop 13 base into a new house. A South Valley buyer can be right about the sale price and still be wrong about the monthly payment if the tax bill is guessed too low.
The calculator below is built around the questions we keep hearing from Morgan Hill, Gilroy, and San Martin homeowners. What will my annual bill look like after reassessment. What happens under Prop 19. How much does an over-55 base transfer save. What does a supplemental bill do after closing.
The old owner and the new owner can live in the same house and pay very different tax bills. Prop 13 caps assessed-value growth while the home is held, so a longtime Morgan Hill owner may have a bill tied to a 1990s purchase price. A new buyer usually starts again at the current purchase price. On a $1.5 million home, that gap can be several thousand dollars a year.
That is why property tax belongs near the start of the decision, not after escrow opens. It affects what you can afford, what you can keep, whether a family transfer works, and whether selling one home to buy another actually helps.
Santa Clara County tax bills start with the 1 percent Prop 13 base rate, then add voter-approved bonds and parcel-level charges. The exact number changes by Tax Rate Area, but a planning estimate near 1.10 percent to 1.20 percent is usually the right starting lane for South Valley homes. Morgan Hill and Gilroy parcels can also carry school bond or Mello Roos charges that do not show up in a simple statewide rule of thumb.
For inheritance planning, the calculator uses the current Prop 19 parent-child exclusion cap and asks whether the heir will make the home a primary residence. For over-55 moves, it compares the old assessed value with the replacement home value so you can see the difference between a transferred base and a fresh reassessment.
Property tax is one part of the homeowner math. If you are selling, start with the net proceeds calculator so the sale price turns into take-home cash. If you are trying to decide whether to hold the house, run the home value estimator first. If the next move is a remodel, rental unit, or family housing plan, the ADU calculator will show whether the added square footage changes the bill enough to matter.
None of these tools replace a tax professional, estate attorney, lender, or assessor review. They give you a grounded first pass so the next call starts from a real number instead of a guess.
Use the South Valley real estate hub when the tax number changes the move. Use the South Valley Directory when the next question is a repair, remodel, or local service call.