sf-appeal 0.1.0

SF Prop 8 Property Tax Appeal Tool — Analyze your property value against comparable sales and generate professional appeal reports.

Appeal

SF Prop 8 Property Tax Appeal Tool — Analyze your San Francisco property's assessed value against recent comparable sales and generate a professional appeal report.

Under California Proposition 8, if your property's current market value has declined below its assessed value, you can request a temporary reduction in your property tax assessment. This tool automates the comparable sales analysis that supports such an appeal.

What It Does

1. Looks up your property from the SF Assessor's records (address, sqft, bedrooms, assessed value)
2. Finds comparable recent sales near your property using multiple data sources
3. Applies adjustments for differences in size, bedrooms, bathrooms, age, and lot size
4. Calculates an estimated market value using the median adjusted price per square foot
5. Generates a PDF appeal report with your comps, adjustment grid, written rationale, and filing instructions

Installation

pip install appeal

For PDF report generation (recommended):

pip install 'appeal[pdf]'

Note: PDF output requires WeasyPrint, which needs system libraries. On macOS: brew install pango. On Ubuntu/Debian: apt install libpango-1.0-0 libpangocairo-1.0-0.

Optional: RentCast API Key

For additional comparable sales data beyond Redfin and DataSF, you can configure a RentCast API key (50 free calls/month):

appeal config
# or set the environment variable directly:
export RENTCAST_API_KEY=your_key_here

Usage

Interactive Mode

appeal

Walks you through entering your address, choosing a search radius, reviewing your property details, and generating a report.

Direct Commands

# Full analysis with PDF report (default)
appeal report "123 Main St"

# Specify search radius and number of comps
appeal report "123 Main St" --radius 1.0 --comps 5

# Markdown output instead of PDF
appeal report "123 Main St" --format md

# Use a specific style seed (same seed = same visual style)
appeal report "123 Main St" --seed myseed123

# Just look up property details
appeal lookup "123 Main St"

# Just find comparable sales (no valuation)
appeal comps "123 Main St" --radius 0.75

# Quick analysis without report file
appeal analyze "123 Main St"

# Show filing deadlines and instructions
appeal info

Command Reference

Command	Description
appeal	Interactive guided analysis
appeal analyze <address>	Analyze property and show valuation
appeal lookup <address>	Look up property details only
appeal comps <address>	Find and display comparable sales
appeal report <address>	Full analysis with PDF/Markdown report
appeal info	Filing deadlines, forms, and instructions
appeal config	Configure API keys

Report Options

Option	Default	Description
--radius	0.5	Search radius in miles
--months	12	How far back to search for sales
--comps	5	Number of comps to select
--format / -f	pdf	Output format: pdf or md
--seed / -s	auto	Style randomization seed
--output / -o	auto	Output file path

How It Works

Data Sources

• SF Assessor (DataSF) — Property details, assessed values, and characteristics via the SF Open Data API
• Redfin — Recent comparable sales with sale prices, dates, and property details
• RentCast (optional) — Additional comparable sales data for broader coverage
• Census Geocoder — Address geocoding for distance calculations

Comp Selection

Comparable sales are selected using a radiate-outward strategy:

1. Sales are grouped into distance rings from your property (0-0.25mi, 0.25-0.5mi, 0.5-1.0mi, etc.)
2. From each ring, the best statistical match with the lowest adjusted price is selected
3. Remaining slots are filled from the global pool, prioritizing the cheapest well-matched comps
4. Property types are matched: SFR with SFR, condo/TIC with condo/TIC, multi-family with multi-family

Adjustments

Each comp is adjusted for differences from your property:

• Size (living area sqft) — scaled by price per sqft
• Bedrooms — +/- per bedroom difference
• Bathrooms — +/- per bathroom difference
• Lot size — proportional adjustment for SFRs
• Building age — per year of age difference

Valuation

The median adjusted price per square foot across selected comps is used (more robust than mean against outliers). This is multiplied by your property's living area to estimate market value.

PDF Styling

Each PDF report is generated with randomized formatting (fonts, colors, table styles, heading styles, spacing) so that no two reports look identical. A deterministic seed controls the randomization — the same seed always produces the same visual style. The default seed is based on your parcel number and the current date.

Filing Your Appeal

Informal Review (Free) — Deadline: March 31

1. Go to online.sfassessor.org
2. Select "Decline in Value"
3. Enter your parcel number and upload your report
4. Include the written rationale in the Comments field

Formal Appeal ($120) — Deadline: September 15

1. File at sfgov.org/aab
2. Submit Application for Changed Assessment (BOE-305-AH)
3. Include your report as supporting evidence

Development

git clone https://github.com/your-org/appeal.git
cd appeal
python -m venv .venv
source .venv/bin/activate
pip install -e '.[dev,pdf]'

Run tests:

pytest

License

MIT

Disclaimer

This tool is for informational purposes only and does not constitute professional appraisal advice. Consult a licensed appraiser for a formal valuation. Tax laws and filing procedures may change — verify current deadlines with the SF Assessor's Office.