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California · R&T Code §§75.10, 75.11California supplemental tax bill: the second bill buyers don't expect

When a California property changes ownership, the assessor appraises it at full cash value on the date of the change – the new base year value (Rev. & Tax. Code §75.10). The difference from the old value is billed on the supplemental roll for the rest of the fiscal year; a purchase between January 1 and May 31 produces two supplemental assessments (§75.11). Ask the lender whether its escrow will pay them or the owner must. The buyer's homeowners' exemption – $7,000 of value for an owner-occupied principal residence (§218) – is claimed by February 15, or by December 10 for 80% of it (§§255, 275).

What changes and why

  1. New base year value

    Full cash value on the date of the change in ownership (§75.10(a)).

  2. Supplemental bills

    Difference between new and old value for the rest of the fiscal year; two bills for purchases January 1–May 31 (§75.11).

  3. Homeowners' exemption

    $7,000 of full value; not for rentals, vacant, second homes (§218).

  4. Claim deadline

    February 15; late claim by December 10 gives the lesser of $5,600 or 80% (§§255, 275).

What the buyer files and when

  • Set money aside for the supplemental bill – it can arrive months after closing.
  • Ask the lender whether supplemental bills are paid from escrow or by you.
  • File the homeowners' exemption claim with the county assessor by February 15.
  • Budget future taxes from the purchase price, not the seller's Proposition 13 value.

The budgeting trap

  • The seller's tax bill reflects the seller's exemptions and capped value – not what the buyer will pay.
  • Escrow for taxes is set from that bill, so the payment can jump after the first year.
  • Exemptions do not move with the deed: the buyer has to apply.

Questions buyers ask

What is a supplemental tax bill in California?

A bill for the increase from the old assessed value to the new base year value set at purchase, prorated for the rest of the fiscal year (§§75.10, 75.11).

Why did I get two supplemental bills?

Purchases between January 1 and May 31 produce two supplemental assessments: one for the current roll and one for the roll being prepared (§75.11(a)).

How much is the California homeowners' exemption?

$7,000 of the full value of an owner-occupied principal residence (§218).

Related guides

Add the buyer's exemption filing to the post-closing checklist as a task with an owner and due date in ClosingCode, so the reminder goes out before the deadline.

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Source: California Revenue and Taxation Code §§75.10, 75.11, 218, 255 and 275 (leginfo.legislature.ca.gov, read October 25, 2026).

General information, not legal or tax advice. ClosingCode is software; it is not a law firm or brokerage.