The roll you are not looking at
Almost everything written about property tax appeals concerns real property: land and buildings, Proposition 13 base years, decline in value. That is where the money is, and it is not the whole roll.
San Diego County also assesses tens of thousands of business personal property accounts — equipment, fixtures, machinery, and the rest of what a business owns and uses. Those assessments arrive through a different process, are built from information the taxpayer supplied, and can be appealed.
They usually are not. A real property assessment arrives as a number handed to you by the county, which invites scrutiny. A business personal property assessment is often derived from your own filed statement, which does not — most people do not audit a number they believe they produced.
Why a self-reported number still goes wrong
The reporting form asks for cost, and the assessor applies valuation factors by category and age to arrive at a value. Several ordinary things break that chain:
- Assets that left and were never removed. Equipment sold, scrapped, or written off stays on the schedule until someone takes it off. It keeps being valued every year.
- Leased equipment reported by both parties. The lessor reports it and so does the lessee, and the same asset is assessed twice.
- Capitalized costs that are not the asset. Freight, installation, and sales tax are frequently reported into cost basis in ways that overstate what the category factor was designed to value.
- Category placement. A factor table treats a general-purpose asset differently from a specialised one, and an asset entered in the wrong class carries the wrong depreciation curve for its whole life.
- Obsolescence the tables do not know about. Standard factors describe normal decline. They do not know that a specific machine was superseded, that its output has no current market, or that its replacement cost has fallen.
None of those are exotic. They are bookkeeping drift, and they compound because the same schedule rolls forward year after year.
Boats, aircraft, and the rest of the unsecured roll
San Diego also assesses thousands of vessels and aircraft. These are valued on their own evidence — condition, hours, market comparables — and an owner who has never seen the basis for the number may simply never have asked.
For aircraft in particular, apportionment and situs questions can matter: where the asset is habitually located and how its use is allocated are factual questions with documentary answers.
The dates, and a different clock for supplementals
The regular assessment appeal period for San Diego County is July 2 through November 30, 2026, filed with the Clerk of the Board of Supervisors, Assessment Appeals, at 1600 Pacific Highway, Room 402, San Diego. November 30, 2026 falls on a Monday, so no weekend extension applies this year.
Supplemental and escape assessments are not on that calendar. They generally run 60 days from the notice, which means an assessment arriving in spring can have a deadline that expires long before the regular window even opens. An owner waiting for "appeal season" to deal with a supplemental notice will be late.
Our San Diego county guide links the Clerk of the Board's own pages.
Evidence has a time limit in California
One rule surprises owners assembling a file: an Assessment Appeals Board cannot consider a comparable sale that occurred more than 90 days after the valuation date. For a January 1 lien date, that puts the usable window at roughly January 1 through the end of March, with earlier evidence admissible but requiring adjustment.
Late-summer market data showing a decline does not help a January 1 assessment. Evidence has to be dated to the lien, and gathering it late is one of the more common ways a real case fails on the record.
Before filing
A California Assessment Appeals Board equalizes by reducing or increasing an assessment under Revenue and Taxation Code section 1610.8. We screen for that exposure before filing, do not file where we see it, and withdraw if it emerges.
To have your San Diego assessments — real property and business personal property alike — checked against the county's own records, start a free analysis. Any estimate is based on county assessment data and public records and is not a guarantee of an outcome.