Supplemental, Escape & Corrected Bills

Triggered by: Change in ownership or completion of new construction after the Jan 1 lien date. The assessor first mails a Notice of Supplemental Assessment (R&T §75.31); the tax collector mails the supplemental tax BILL weeks or months later. The notice and the bill are distinct documents — in most counties the appeal clock runs from the NOTICE, not the bill.

Appeal window: 60 days from the mailing date printed on the Notice of Supplemental Assessment or its postmark, whichever is later. EXCEPTION: in counties whose board of supervisors adopted R&T §1605(c), and in Los Angeles County, the 60 days runs from the mailing date printed on the supplemental TAX BILL (or its postmark, whichever is later). If the notice was not received at least 15 days before the deadline, the owner may file within 60 days of the tax bill's mailing/postmark with an affidavit of non-receipt.60 days

Supplemental tax is prorated from the first day of the month following the event date to the end of the fiscal year (June 30) and is IN ADDITION to the regular annual bill — it is not forwarded to most mortgage impound accounts. If the event occurs Jan 1-May 31, TWO supplemental assessments/bills issue (one for the remainder of the current fiscal year, one for the full upcoming fiscal year, §75.41). If the new value is lower than the prior value, a negative supplemental assessment produces a refund. Supplemental bill delinquency dates float based on the month the bill is mailed (§75.52). Owners can also request an informal review with the assessor's office before or instead of filing a formal appeal, but the informal review does NOT extend the 60-day formal filing deadline.

Triggered by: Property or value that escaped assessment or was underassessed for a prior year — e.g. unreported/unrecorded change in ownership, unpermitted or unreported new construction, business personal property audit findings, or exemption incorrectly allowed.

Appeal window: 60 days from the date of mailing of the notice of enrollment of the escape assessment (R&T §1605(b)); escape assessments are excluded from the regular assessment-period filing window. In §1605(c) counties and Los Angeles County, 60 days from the mailing date printed on the tax bill or postmark, whichever is later.60 days

Back-year reach: 4 years after July 1 of the assessment year in which the property escaped (§532(a)). 8 years for unrecorded changes in ownership where no change-in-ownership statement was filed, and for escapes carrying the §504 25% underreporting penalty (§532(b)). NO time limit where the §503 fraud/collusion penalty applies, or for legal-entity ownership changes where the required §480.1/§480.2 statement was never filed.

Escape bills can stack several back years at once. If the escape taxes exceed $500, the owner may elect a 4-year installment payment plan (§4837.5). Interest (and penalties of 10-25% for failure to report, 75% for fraud) may be added. Paying the bill does not waive appeal rights, and appealing does not excuse timely payment.

Triggered by: Assessor-discovered errors. §51.5: errors in a base year value NOT involving the assessor's judgment as to value (clerical, factual) may be corrected in ANY year the error is discovered; errors involving value judgment may only be corrected within 4 years after July 1 of the assessment year the base value was first established. §4831: other roll entry errors not involving value judgment correctable within 4 years after the assessment was made (1 year for certain tax-collector errors).

Appeal window: If a correction INCREASES the assessment, it is enrolled and noticed as an escape assessment, giving the owner the standard 60-day appeal window from the notice (or bill in §1605(c)/LA counties). Downward corrections generate a corrected bill or refund; the owner may also appeal a §51.5 base-year value determination within the normal appeal periods.60 days

Back-year reach: §51.5(a) non-judgment errors: unlimited (correctable whenever discovered, applied prospectively plus escape/refund years within limitation periods); §51.5(b) value-judgment errors: 4 years from July 1 of the year the base value was established; §4831: 4 years after the assessment date.

A homeowner who spots a factual error (wrong square footage, wrong base year, double assessment) can request a §51.5/§4831 correction directly from the assessor at any time without a formal appeal — this is often faster than the appeals board and, for non-judgment errors, is not limited to the current year.

Triggered by: Taxes paid that were erroneously or illegally collected, or overpaid due to roll corrections, cancellations, or a successful assessment reduction.

Appeal window: Claim must be filed within 4 years after making the payment, or within 1 year after the mailing of a notice of overpayment by the tax collector/auditor, or within the period agreed to in a written extension — whichever is later. A timely assessment appeal application can be designated as a claim for refund.

Back-year reach: 4 years from date of payment

If a refund claim is denied or not acted on within 6 months, the taxpayer may file a refund action in superior court (§5141: within 6 months of denial). Refunds from corrections under §4831/§§4876-4877 can be processed by the auditor without a claim (§5097.2).