Informal Assessor Review vs. Formal Appeal: Which One Should You File?

There are two ways to ask California to lower your assessed value, and homeowners routinely pick the wrong one — usually because the free option is easier to find and they don't realize it comes with no deadline protection at all.

Two different doors

Informal review (often called a decline-in-value request or Prop 8 request) is a direct ask to the Assessor's Office. Free, usually a short online form, no hearing. The assessor looks at your sales data and either adjusts the value or doesn't. There's no appeal from the answer and no independent body involved.

Formal appeal goes to the Assessment Appeals Board — a panel independent of the assessor, with a hearing, a record, and a decision the assessor must implement. It has a statutory filing window and, in some counties, a fee.

The windows don't line up, and that's the trap

The informal window usually opens and closes before the formal one, and it varies by county:

• San Francisco: informal review runs January 2 – March 31, free, and covers single-family homes, condominiums, townhouses, live-work lofts, and co-op units. Results arrive by Notice of Assessed Value in July. The formal AAB appeal runs July 2 – September 15 and costs $120.
• Alameda County: informal decline-in-market-value requests are accepted July 1 – December 31, free. The formal window still closes September 15.
• Santa Clara and Contra Costa both offer their own informal Prop 8 request forms on the assessor's site.

Here is the failure mode. You file an informal request in the spring, wait, and get your answer in July. You disagree — but by then you may have weeks, not months, to file formally, and if your county closes September 15 that clock is short. Filing informally does not extend, pause, or preserve the formal deadline.

So: which one?

File informally if the gap between assessed and market value is obvious and easily documented, it's early in the year, and you'd rather not pay a fee or attend a hearing. In a clearly declining market this often just works.

File formally if any of the following is true:

• The informal window for your county has already closed for the year. (In San Francisco, anything after March 31 means the formal appeal is your only route this year.)
• Your case involves judgment — condition issues, a disputed square footage, a property type where comp selection is arguable.
• The amount at stake is large enough that a $120 fee is noise. (Roughly what's at stake.)
• You want the burden of proof on the assessor, which only happens at a hearing.

The safest play if you're near the deadline: file formally, then keep talking to the assessor. Most appeals never reach a hearing — the assessor's office reviews the file, and if your comps are solid they'll often propose a stipulated value you can accept, which withdraws the appeal. You get the informal outcome with the formal deadline protected. That's the version experienced filers use.

Both doors need the same evidence

Neither process cares how you feel about your bill. Both want arms-length sales of genuinely comparable properties close to the January 1 valuation date — and under §402.5, nothing dated more than 90 days after the lien date. Same comps, same analysis, whichever door you use. (How to build that set.)

CompFinder produces the comp set and the written comparison for SF, Oakland, San Jose, Seattle, and Issaquah, which is the input either process is asking for.

If you're reading this in August

The informal window has closed in San Francisco. Alameda's is open but won't protect you. In San Francisco, Oakland, and San Jose the formal deadline is September 15 — check your county's exact date and file.