The Supplemental Property-Tax Bill That Shows Up After You Buy or Sell

A few months after closing, a California buyer often gets a tax bill they did not see in the monthly mortgage estimate. Sellers sometimes get one too, for the months they still owned the house. That bill is the supplemental assessment.

Under Proposition 13, a sale generally resets taxable value toward the purchase price. The regular tax bill on the roll may still show the old owner’s value until the next fiscal year. The county bills the difference for the rest of the year in a supplemental bill.

Why escrow did not “cover” it

Escrow prorates the regular tax bill between buyer and seller as of the closing date. That proration uses the bill that exists, which is often still based on the old assessed value. It does not prepay the supplemental that the assessor has not issued yet.

If your lender escrows taxes, the impound account may not be large enough for the supplemental when it arrives. Budget for it in cash. Ask the county tax collector how supplemental bills are mailed so it does not sit in a pile of junk mail.

Sellers are not automatically done

If you sell mid-year, you can still owe supplemental tax for the period you owned the home after the value changed, depending on the dates. Read the bill. The fiscal year in California runs July 1 through June 30, which confuses people who think in calendar years.

Do not ignore a supplemental bill because you already “paid taxes at closing.” Unpaid property tax becomes a lien. If you are unsure which owner owes which days, call the tax collector with the parcel number and the recording date before you pay the wrong amount or pay it twice.

What to ask before you close

Buyers should ask their agent and escrow for a rough supplemental estimate using the purchase price and the current assessed value. It will not be perfect, but it stops the surprise.

If you are transferring a base-year value under Proposition 19, the supplemental math changes. Do not use a generic estimate. Use the assessor’s figure for that claim.

Before you act

By Nick Valmores, NJV Realty. This is general education for California residents, with examples from the Inland Empire, the San Gabriel Valley, Los Angeles, and Orange County. It is not legal, tax, lending, or insurance advice. City rules, county custom, and program details change. Confirm your situation with a California-licensed real estate broker and, when money, title, tax, or insurance is involved, with your own attorney, CPA, lender, or insurance broker. Equal Housing Opportunity.