DIY California Property-Tax Appeal: Decline-in-Value (Prop 8)

What this is: A plain-English playbook to file and win a decline-in-value appeal.
Who it’s for: Any California homeowner. No legal or appraisal background required.
Core idea: Show that your home’s fair market value on January 1 (the lien/valuation date) is lower than the value on the tax roll.

Quick overview (what you’ll do)

Gather your property facts.
Find 3–4 recent, similar sales (“comparables” or “comps”).
Check sale dates: on/before Jan 1 or no more than 90 days after Jan 1.
Build a simple comp grid and compute $ per square foot.
Make small, sensible adjustments for differences (size, lot size, condition, amenities).
Reconcile one market value number for January 1.
Fill the county appeal form (BOE-305-AH or county equivalent) and submit on time.
Bring your packet to the hearing and present calmly.

What you’ll need

Your assessment notice or tax bill (for parcel number and the roll value).
Basic facts about your home: living area (sq ft), lot size, beds/baths, year built, parking, condition.
3–4 comparable sales (addresses, sale dates, living area, lot size, beds/baths, condition, sale prices).
A simple spreadsheet (Excel/Sheets) or calculator.

Step 1 — Confirm the appeal type

You are filing a Regular Assessment – Decline in Value appeal.
That means you are estimating market value on January 1 of the appeal year.

Step 2 — Check sale-date rules (very important)

Allowed: Sales that closed on or before January 1, and sales that closed within 90 days after January 1 (i.e., up to March 31).
Not allowed: Sales that closed more than 90 days after January 1 (those cannot be considered).
Closer to Jan 1 is better. If you use older pre-Jan-1 sales, you’ll explain any market trend briefly.

Step 3 — Collect your property facts

Confirm your home’s:

Living area (sq ft) — exclude garage/porches.
Lot size (sq ft) — use total lot size; if part is unusable, note it.
Beds/Baths, Year built, Parking, notable features (view, deck, A/C).
Condition (choose one): Excellent / Good / Fair / Poor.

These will guide your comp selection and adjustments.

Step 4 — Find your comps

Pick 3–4 arm’s-length sales that are physically similar:

Within a sensible distance (often ≤ 1 mile in cities; farther in rural areas).
Similar living area (ideally within ±15–25%).
Similar lot size (ideally within ±20–40%; explain if larger).
Similar beds/baths, year built, condition, and amenities (parking, view, etc.).
Sale dates on/before Jan 1 or within 90 days after.

If perfect comps don’t exist, choose the best available and explain differences.

Step 5 — Build a simple comp grid

Create a one-page table with the subject and your comps:

Field	Subject	Comp #1	Comp #2	Comp #3	Comp #4
Address
Distance (mi)
Sale Date	–
Living Area (sf)
Lot Size (sf)
Year Built
Beds / Baths
Condition
Features (parking, view, deck, A/C)
Sale Price	–
$ / sf (Sale Price ÷ Living sf)	–

Tip: Add a small map and a photo of each property (curb shots) to show similarity.

Step 6 — Make basic adjustments (keep them simple)

Adjust each comp to better match your subject (never adjust the subject). Use round numbers and brief notes.

Time/market movement: If the market rose or fell between the comp’s sale date and Jan 1, apply a small % up or down and say why (e.g., “local index shows ~1%/month decline in Q4; applied −2%,” or “used closers sales so no time adjust”).
Living area (size): If comp is larger than subject, adjust down; if smaller, adjust up. A simple rule: multiply the sq-ft difference by a conservative marginal $/sf (often 50–75% of the average $/sf of your comps).
Lot size: Bigger lots tend to be worth more, but with diminishing returns. Apply a modest dollar add/subtract for notable differences, especially when the lot affects utility (yard, parking, ADU potential). If uncertain, explain qualitatively and keep the adjustment small.
Condition/Amenities: If the comp is clearly superior (newer remodel, view, garage), adjust down; if inferior, adjust up. Keep adjustments conservative unless you have strong evidence.

Add a row to your grid (or a notes column) showing each adjustment and the Adjusted Sale Price.

Step 7 — Reconcile one value for January 1

Compute Adjusted $/sf for each comp: Adjusted Sale Price ÷ Comp Living sf.
Use the median of those adjusted $/sf figures.
Multiply by your subject living area to get your indicated value on January 1.
Sense-check: your final value should sit comfortably among the adjusted comp prices. If one comp is an outlier, rely more on the others and say why.

Example:
Adjusted $/sf of three comps = $1,050, $1,020, $1,060 → average $1,043/sf.
Subject living area = 1,140 sf → $1,043 × 1,140 ≈ $1,189,000 (rounded).

Step 8 — Fill the appeal form (BOE-305-AH or county version)

Column A (“Value on Roll”): copy the county’s numbers from your notice/bill.
Column B (“Applicant’s Opinion of Value”): enter your Total (the reconciled value from Step 7).
Land vs Improvements breakout (easy method): keep the same proportion the county uses in Column A, applied to your lower Total.

Quick formula for the breakout:

A_total = A_land + A_improvements
landShare = A_land / A_total
B_total = your reconciled value
B_land = round(B_total × landShare)
B_improvements = B_total − B_land

If the roll shows Land = 0 (common for condos), set B_land = 0 and B_improvements = B_total.

Don’t overfill: Lines like Fixtures/Personal Property/Mineral Rights are typically blank for a house.

Step 9 — File on time and keep proof

Regular appeals are usually filed mid-summer to mid-September (many counties use July 2 – Sept 15). Some counties use different dates—check your county.
File online or by mail as your county allows. Save confirmations, receipts, and a full copy of your application.

Important: Keep paying your tax bill on time during the appeal. If you win, the county refunds the difference.

Step 10 — Prepare for the hearing

Bring three copies of:

Your completed application,
Your comp grid and calculations,
Photos and a small map,
Any brief explanation of adjustments and how you reconciled your value.

How to present (short script):

“I’m appealing the regular assessment as a decline-in-value. Using three arm’s-length sales within about half a mile, all on/before January 1 or within 90 days after, and adjusting for living area, lot size, and condition, the indicated value on January 1 is $____. That’s below the roll value of $____. I’m requesting the roll be reduced to my indicated value.”

The board may ask simple follow-ups (e.g., “Why is Comp #2 a good match?”). Keep answers short and factual.

One-page checklist

Appeal type: Regular – Decline in Value.
Jan 1 valuation date set.
Sale dates: all comps on/before Jan 1 or ≤ 90 days after.
3–4 good comps selected (distance, size, lot size, condition, amenities).
Comp grid built; $ per sf computed.
Simple adjustments applied (time, size, lot, condition, amenities).
One reconciled value for Jan 1 (rounded).
Form filled: Column A (roll), Column B (your value), land/improvements breakout.
Filed within the county’s window; proof saved.
Hearing packet assembled; short script practiced.
Keep paying taxes on time while appeal is pending.

Templates

A) Comp grid (paste into your sheet)

Columns:

Address	Distance(mi)	SaleDate	LivingSF	LotSF	YrBuilt	Beds	Baths	Condition	Features	SalePrice	$/SF	TimeAdj	SizeAdj	LotAdj	Cond/AmenAdj	AdjustedPrice	Adjusted $/SF

B) Land/Improvements breakout (example)

Column A (roll): Land $700,000; Improvements $1,000,000 → Total $1,700,000 → landShare = 41.18%.
Your reconciled total (Column B Total): $1,600,000
Column B Land: $1,600,000 × 41.18% ≈ $659,000
Column B Improvements: $1,600,000 − $659,000 = $941,000

Tips and common pitfalls

Don’t use sales more than 90 days after Jan 1. The board can’t consider them.
Lot size matters. If a comp’s lot is much larger/smaller, mention it and adjust modestly.
Avoid “perfect-looking” but odd comps. Estate sales, fixers, and off-market deals can distort prices—explain or avoid.
Be conservative. If you can support a range, take the midpoint; boards reward reasonableness.
Keep everything simple and transparent. Plain math and brief notes beat complex models at a hearing.

You’ve got this

If you can: (1) show 3 good comps, (2) explain a few simple adjustments, and (3) present one clear number for January 1, you’re doing exactly what the appeals board expects.