Homeowner Summary

Property & Value Snapshot

Your Property

Address: 391 Portofino Dr, San Carlos, CA 94070

Opinion of Value on Lien Date

AppealArc's opinion of your property value on lien date (January 1, 2025) is $2,070,000, at about $1,095 per square foot.

This valuation draws from five nearby sales that closed between November 14, 2024 and January 9, 2025 (see Exhibit A: Comparable Sales). Each comparable was carefully adjusted for living area differences, school district variations, location and walkability factors, as well as bathroom and garage differences (see Exhibit B: Adjustments). The analysis takes a comprehensive approach, avoiding aggressive view premium claims and ensuring a defensible and market-grounded valuation.

Expected Tax Savings

Your Current Assessment

Your enrolled value is tied to the factored base‑year value from your purchase on October 22, 2021 at $2,420,000. Under Proposition 13, this value increases by up to 2% per year.

Estimated Current Assessed Value

We can derive your current assessed value using simple compounding from your purchase date. Note that the actual assessed value may vary slightly, so check your tax bill or county records.

Annual Tax Savings Calculator

Formula: Savings = (Current Assessed Value − Opinion of Value on Lien Date) × 1.18%

Note: 1.18% is the approximate effective tax rate for San Mateo County. Your exact rate may vary slightly by tax assessment area.

Example Calculation

Assuming assessed value of $2,619,000 (four 2% factors):

Current Assessment:        $2,619,000
Opinion of Value:        − $2,070,000
                         -------------
Difference:                $  549,000

Annual Savings:
$549,000 × 1.18% = $6,478 per year

What This Means for You

• One-time reduction for the 2025-26 tax year. Can be renewed annually if market value remains below your Prop 13 track.
• Saves approximately $5,900 to $6,500 in annual property taxes
• Your factored base-year value track (Prop 13) continues unchanged
• Prop 8 reductions are temporary. When market values rise, your assessment can increase by more than 2% per year until it returns to your Prop 13 track.

Filing Guide

How to File the Informal Review Now

Good luck with your appeal! The evidence is strong, the methodology is sound, and you have a well-supported case for a temporary Prop 8 reduction.

Step 1: Bundle Your Exhibits

Gather all exhibits included in this package:

• Letter to the Assessor: date and sign.
• Exhibit A: Comparable Sales
• Exhibit B: Adjustment Grid

Step 2: Submit to the Assessor

Submit the online form at the San Mateo County Assessor. Your submission will set in motion a review of Decline in Market Value (Proposition 8) for your property.

Timeline & What to Expect

Informal Review Process

If Informal Review Is Unsuccessful

Frequently Asked Questions

Can my taxes go up more than 2% after this reduction?

Yes. Proposition 8 reductions are temporary and reviewed annually. When market value rises above the reduced assessment, your taxes can increase by more than 2% per year until your assessment returns to your Prop 13 track. However, your assessment can never exceed your Prop 13 factored base-year value track. Your Prop 13 base is protected. This reduction does not reset your acquisition value. Your Prop 13 base continues to grow at up to 2% per year regardless of temporary Prop 8 reductions.

What if I miss the formal appeal deadline?

You cannot appeal that year's regular roll value. Options: a) Wait for next year's filing window, or b) Appeal only if you receive a Supplemental or Escape assessment (60-day window from notice)

Will this affect my Prop 13 base?

No. Prop 8 reductions are temporary and do not reset your base year value from your October 2021 purchase.

Do I need a lawyer or appraiser?

For Proposition 8 informal review: No. This package provides everything you need.
For formal appeal: Not required but can be helpful for complex cases or high-value properties. You can represent yourself using these exhibits, but AppealArc cannot assist with formal appeals.

Methodology

All comparable sales data is sourced from public records, including Redfin listing pages, Zillow property records, MLS data where available, and county assessor records. Distances shown are approximate straight-line measurements for orientation only, so actual driving distances may vary.

The methodology here follows the county's comp-selection guidelines (same area, similar size and condition, within roughly 90 days after lien date), Board of Equalization best practices (comparable sales, transparent adjustments, lien date focus), and Assessment Appeals Board expectations (clear evidence, defensible methodology, market-based adjustments).

Keep in mind this is an opinion of value based on market data analysis, not a formal appraisal. The final assessed value is determined by the San Mateo County Assessor during informal review, or by the Assessment Appeals Board if you proceed to a formal appeal.

Questions or Need Help?

This package contains everything you need to file your appeal. If you have questions about the process or need additional support:

• Review the Knowledge Base: AppealArc KB
• County-specific guidance: San Mateo County Guide
• Email support: [email protected]

Letter to the County Assessor

This letter is formatted and ready to submit as-is. Simply add today's date and your signature.

---

Office of Assessor-County Clerk-Recorder
San Mateo County, California

MM/DD/YYYY

    Re: Decline in Value of Property at 391 Portofino Dr, San Carlos, CA 94070

Dear Assessor:

I respectfully request an informal Proposition 8 (decline‑in‑value) review for the above property for the 2025–26 roll year.

My opinion of Market Value as of January 1, 2025 is $2,070,000. This value:

• Equals approximately $1,095 per square foot, consistent with the adjusted comparables
• Falls below the more desirable downtown properties after accounting for their location premiums
• Reflects that the subject's sloped lot has limited utility compared to flatter, more walkable properties

I have attached for your review the following exhibits:

• Exhibit A: Comparable Sales
• Exhibit B: Adjustment Grid

The exhibits review the features of my property, examine comparable sales with detailed adjustments for differences in size, location, and amenities, and explain how the comparable sales inform my opinion of my property value.

Thank you for your consideration of this informal review. I am available to provide any additional information or clarification you may need.

Sincerely,

[Your Signature]

Homeowner
391 Portofino Dr San Carlos, CA 94070

Exhibit A: Comparable Sales

Subject Property Summary

Address: 391 Portofino Dr, San Carlos, CA 94070

391 Portofino Dr is a single‑level 3‑bed, 2‑bath, 1,890‑sq‑ft home (1961) in the San Carlos Hills, offering sweeping Bay and Mount Diablo views. Living, dining, and family rooms feature vaulted ceilings and walls of glass around a gas‑log fireplace. Outdoor spaces include a wraparound deck, private patio, and terraced garden on a 0.44‑acre hillside lot. Practical touches: double‑pane windows, composition roof, automatic sprinklers, and a 2‑car garage. Convenient to I‑280, parks, and downtown San Carlos. Elementary School District: San Carlos Elementary. High School District: Sequoia Union High. Heating and cooling are central forced air.

Comparable Sales

All comparables are within ~2 miles and bracket the subject in size/condition. Four closed within 9 days of the lien date (Jan 1, 2025) and one closed ~48 days prior, consistent with AAB practice and AppeaLarc guidance. Distances are straight-line estimates from 391 Portofino (approx.). Price-per-sf is Sold Price ÷ Living Area.

Comparable Sales Summary Table

Exhibit B: Adjustment Grid

Adjustment Methodology

All adjustments normalize each comparable to the subject property. Positive amounts increase a comp's price to reflect a feature the subject has and the comp lacks; negative amounts reduce a comp's price for superior comp features.

Adjustment Rates Applied

Please see the Appendix for the detailed derivation of the adjustment rates.

Detailed Adjustment Grid

Summary Table

Comp 1: 1318 Crestview Dr

Comp 2: 10 Granite Ct

Note: Redwood City Elementary typically trades lower than San Carlos Elementary; the +3% normalization accounts for this school district difference.

Comp 3: 1374 Orange Ave

Note: White Oaks/downtown location commands a walkability premium; faster absorption and higher list-to-sale ratios observed in this pocket.

Comp 4: 50 Pine Ave

Comp 5: 2025 Brittan Ave

Note: Brittan Avenue's proximity to downtown carries a modest walkability premium.

Value Reconciliation

The five adjusted sales indications range from $2.02M to $2.53M, with the low end anchored by 2025 Brittan Ave at $2,016,500 and the high end by 1318 Crestview Dr at $2,530,900.

In this analysis, the greatest weight is assigned to 2025 Brittan Ave ($2,016,500), 50 Pine Ave ($2,065,250), and 1374 Orange Ave ($2,156,550). These three properties form a consistent lower-indication cluster that most closely brackets the subject. The two hillside comparables—Granite and Crestview—are larger and newer, pushing their adjusted values higher. Meanwhile, the three downtown-adjacent properties benefit from walkability premiums that, even after adjustment, place them in a different market segment than the subject's hillside setting.

Final Opinion of Value

As of January 1, 2025, the final opinion of value is $2,070,000, with approximately $1,095 per square foot.

This value sits between the two most relevant low-indication comparables on a price-per-square-foot basis: 2025 Brittan Ave at $1,099/sf (adjusted) and 10 Granite Ct at $1,098/sf (adjusted). Both properties provide strong support for the conclusion.

Importantly, the opinion falls below the walkable Orange Ave comparable after location, bath, and garage normalization. The subject's larger but sloped lot offers limited utility compared to smaller, flatter lots in more walkable neighborhoods.

Appendix: Deriving the Adjustment Rates

Auditable Framework

Follow appraisal best practice: I built the adjustment grid using the standard sales-comparison approach: pick recent local sales and adjust each for differences (size, time, features, location) to infer the subject's value. Fannie Mae requires adjustments supported by market evidence.

Stay within assessment board rules: California allows only sales up to 90 days after the valuation date for decline-in-value appeals per the California State Board of Equalization. I kept to late-2024 / early-2025 sales.

Quantification methods: Primary method is paired-sales logic with our actual comps. Backup method when pairs are thin is cost-based proxies (depreciated) or percent adjustments for location/schools.

GLA (living area) adjustment = $275 per sf (marginal value)

Larger homes sell for less on a $/sf basis due to diminishing returns. Appraisers use marginal $/sf, not the average shown on listing sites.

Paired-sales evidence: Comparing 50 Pine (1,380 sf, $1,925,000) with 2025 Brittan (1,910 sf, $2,100,000) isolates the GLA difference. Both have 2 baths and 2-car garages. Adjusting for the extra bedroom ($15k), the size-only price gap is $160,000 ÷ 530 sf = $302/sf.

A second cross-check using Redfin data for Crestview vs Brittan confirms these larger homes trade around $1,10x to $1,26x per sf. The marginal rate falls well below the $1,100 average.

I used $275/sf, tempering down from $302/sf for conservatism. AppraisersForum.com notes marginal GLA adjustments typically run one-third to one-half of average $/sf in higher-priced markets.

School district adjustment = +3% (San Carlos Elem. premium over Redwood City Elem.)

Classic research shows public school quality is capitalized into home prices. I'm using the well-accepted direction of the effect, not exact elasticities, keeping our local figure small and conservative at +3%.

10 Granite Ct is in Redwood City Elementary (Zillow shows Clifford K-8), while the subject is in San Carlos Elementary. Public data sources (Niche/GreatSchools) show San Carlos ESD testing outcomes and rankings consistently above Redwood City ESD.

Walkability / micro-location premium = −3% to −5%

I applied −5% for Orange (White Oaks / near downtown) and −3% for Brittan (closer-in, but not as walkable as White Oaks).

Multiple empirical studies find homes in more walkable areas trade at a premium. I used small percentages (3 to 5%) because we're moving within San Carlos, not across a metro area, and should not over-generalize national elasticities to street-to-street comparisons.

The White Oaks / Orange Ave intersection shows a Walk Score of 70 (Very Walkable). Hillside areas similar to the subject rate far lower: Beverly Terrace shows 18, Alder Manor around 14, and the hills show 6 according to Walk Score. This illustrates the large walkability gap between downtown-adjacent streets and the hills.

Redfin's study estimated 0.9% per Walk Score point at the metro level. Applying this locally would overstate differences (a 50-point gap would imply greater than 40% premium, not credible for our micro-set). I capped the effect at 5% for Orange and 3% for Brittan.

Baths = $40,000 per full bath ($20,000 per half-bath)

Clean paired sales for bath differences were scarce, so I anchored to Bay Area remodel costs and used a depreciated, contributory figure (value < cost), a standard fallback when paired data are thin. Angi shows full bath projects commonly in the $20k to $60k+ range. Using $40k (full) and $20k (half) is conservative.

Garage = $25,000 per enclosed space

Paired sales for garage count were thin, so I used a conservative contributory value grounded in build/convert costs. This Old House puts a basic 2-car garage in the $30k to $55k range (more in the Bay Area). $25k per space (below typical new-build cost) is deliberately cautious.

Bedrooms = $15,000 per bedroom

Appraisers often find small or no adjustment between 3 and 4 bedrooms when GLA is similar, since the utility gain is modest and already partly captured by GLA. Sacramento Appraisal Blog reflects this nuance. $15k is conservative and avoids double-counting with GLA.

Cross-check: The Pine vs Brittan pairing that produced $302/sf for GLA assumed $15k for the extra bedroom, maintaining internal consistency.