Three clocks, three triggers
Most owners hold one California property tax date in their head, and in San Bernardino it is November 30. That date is correct for the regular assessment roll and useless for everything else.
The regular period — July 2 through November 30, 2026 — covers the annual roll: your base-year value as factored, or a decline-in-value argument against it. It is predictable, it is long, and it is the one that gets calendared.
The other two are event-driven, and they are shorter.
Supplemental and escape assessments: 60 days
A supplemental assessment issues when a property changes ownership or new construction is completed. It reassesses to market as of that event and bills the difference for the remainder of the year.
An escape assessment issues when the assessor determines that value should have been enrolled in a prior year and was not.
Both run on a 60-day-from-mailing rule in San Bernardino. That matters for two reasons. First, sixty days is short, and these notices arrive in ordinary mail without the seasonal framing that makes an annual notice feel urgent. Second, they arrive whenever the assessor gets to them — which for an escape assessment can be well after the year in question.
The failure mode is specific and common: a supplemental notice arrives in March, gets filed under "deal with at appeal time," and the 60 days expire in May while the owner waits for a July window that has nothing to do with it.
Calamity assessments: six months
Where property is damaged by a misfortune or calamity and the county has the relevant relief mechanism, a reassessment reflecting the damage may issue. In San Bernardino, an appeal of a calamity assessment runs six months from mailing.
Six months is generous relative to sixty days, and it is still a clock that starts on delivery rather than on the calendar. For an owner managing a damaged property, six months disappears quickly.
Which argument goes with which clock
The clocks differ because the questions differ, and matching them matters:
- Regular roll — is the factored base-year value above market on the January 1 lien date? This is the Proposition 8 question.
- Supplemental — was the market value as of the change in ownership or completion of construction correct? The valuation date is the event date, not January 1.
- Escape — should this value have been enrolled at all, and if so at what amount, for the year in question?
- Calamity — does the reassessment properly reflect the damage as of the relevant date?
Filing a decline-in-value argument against a supplemental assessment, or vice versa, wastes the filing. The Contra Costa and Riverside guides describe the same structure in neighbouring counties.
The market context, for the regular roll
San Bernardino carries a large share of the Inland Empire's big-box distribution product, and that market has been correcting: vacancy up through mid-2026, negative net absorption, substantial sublease availability, and asking rents well below the 2023 peak.
For an owner of a large distribution building, that is the Proposition 8 fact pattern. The evidence is the leasing: rent actually achieved net of concessions, real downtime between tenants, and the sublease space competing against yours. Market reports establish that a decline happened; your documents establish what it did to your building.
Note the evidentiary limit that applies statewide in California: a board cannot consider a comparable sale occurring more than 90 days after the valuation date. For a January 1 lien date that closes the usable comparable window around the end of March.
Filing, and the exposure
Appeals go to the San Bernardino County Clerk of the Board / Assessment Appeals Board. Our San Bernardino county guide links the county's own materials.
A California board equalizes the roll 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 it is present, and withdraw if it surfaces later.
To have your San Bernardino assessments checked against the county's own records — including any supplemental or escape notice already in hand — start a free analysis.