ciphertax 0.1.0

Safely use AI for tax filing — redacts PII locally so your personal data never leaves your machine

🔐 CipherTax

Safely use AI for tax filing — your personal data never leaves your machine.

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The Problem: AI + Tax Documents = Privacy Risk

You want to use AI to help with your taxes. You upload your W-2. The AI now has:

• Your Social Security Number
• Your full legal name and home address
• Your employer's EIN
• Your bank account and routing numbers
• Your income, phone number, email

This data is sent to cloud servers. It may be logged, cached, stored for model training, or exposed in a data breach. Under GDPR, CCPA, and other regulations, this creates real compliance risk. For individuals, it creates identity theft risk.

The irony: AI doesn't actually need your SSN to calculate your taxes. It needs your income amounts, filing status, and state — but not your identity.

The Solution: CipherTax

CipherTax is a local-first privacy layer that sits between your tax documents and AI. It:

1. Extracts text from your tax PDFs and photos (digital + scanned/OCR)
2. Detects all personally identifiable information using Microsoft Presidio + custom tax recognizers
3. Replaces identity data with tokens (John Smith → [PERSON_1], 123-45-6789 → [SSN_1]) while keeping financial amounts the AI needs
4. Stores the real values in a locally encrypted vault (AES-256, never uploaded)
5. Sends only the sanitized text to Claude
6. Restores real PII in the AI's response locally

Zero PII ever leaves your machine.

Your Tax PDF (W-2, 1099, etc.)
        │
        ▼
┌──────────────────────────┐
│  1. EXTRACT TEXT          │  ← Runs locally (PyMuPDF + Tesseract OCR)
└──────────┬───────────────┘
           ▼
┌──────────────────────────┐
│  2. DETECT PII            │  ← Runs locally (Presidio + custom recognizers)
│  SSN, EIN, names, emails, │
│  phone, addresses, bank   │
└──────────┬───────────────┘
           ▼
┌──────────────────────────┐
│  3. SMART TOKENIZATION    │  ← Runs locally
│  "John Smith" → [PERSON_1]│
│  "123-45-6789" → [SSN_1]  │
│  "$75,000" → kept as-is ✓ │  Financial data preserved for tax math
└──────────┬───────────────┘
           │
     ┌─────┴──────┐
     ▼            ▼
┌─────────┐  ┌────────────────┐
│ VAULT   │  │ CLAUDE API     │  ← Only tokenized text sent
│ (AES    │  │ (zero PII)     │
│ encrypt)│  │                │
└─────────┘  └───────┬────────┘
     │               │
     └───────┬───────┘
             ▼
┌──────────────────────────┐
│  4. REHYDRATE             │  ← Runs locally — restores real PII
│  [PERSON_1] → John Smith  │
│  [SSN_1] → 123-45-6789    │
└──────────────────────────┘

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What AI Sees vs What You See

Before (Original W-2 — contains PII):

Form W-2  Wage and Tax Statement  2024
a  Employee's social security number: 234-56-7890
b  Employer identification number (EIN): 45-6789012
c  Employer's name: Acme Technology Solutions Inc
e  Employee's name: Maria Elena Rodriguez
   Employee's email: [e-mail]
   Employee's phone: [phone]
1  Wages, tips, other compensation:    $92,450.00
2  Federal income tax withheld:         $16,200.00
15 State: IL

After (What Claude receives — zero PII):

Form W-2  Wage and Tax Statement  2024
a  [ADDRESS_1]'s social security number: [SSN_1]
b  [ORGANIZATION_6] identification number ([ORGANIZATION_8]): [EIN_1]
c  [ORGANIZATION_6]'s name: [ORGANIZATION_7]
e  [ADDRESS_1]'s name: [PERSON_1]
   [ADDRESS_1]'s email: [EMAIL_1]
   [ADDRESS_1]'s phone: [PHONE_1]
1  Wages, tips, other compensation:    $92,450.00    ← KEPT (AI needs this)
2  Federal income tax withheld:         $16,200.00    ← KEPT
15 State: IL                                          ← KEPT

Notice: SSN, name, EIN, email, phone are all replaced with tokens. But financial amounts ($92,450, $16,200) and state (IL) are preserved — Claude needs these to compute your taxes.

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Security In Depth

CipherTax uses multiple layers of defense to prevent PII leakage:

Layer 1: PII Detection (Microsoft Presidio + Custom Recognizers)

• Microsoft Presidio — Industry-standard PII detection engine (7,900+ ⭐ on GitHub), used by enterprises worldwide
• spaCy NER — Named Entity Recognition for person names, organizations, addresses
• Custom tax recognizers — Purpose-built regex patterns with context awareness for:
  • SSN (with IRS-valid format validation)
  • EIN (Employer Identification Number)
  • ITIN (Individual Taxpayer Identification Number)
  • Bank account numbers (with context: "account", "deposit", etc.)
  • Routing numbers (with context: "routing", "ABA", etc.)
  • W-2 control numbers

Layer 2: Smart Tokenization

• Identity data → deterministic tokens ([SSN_1], [PERSON_1])
• Same value always maps to the same token (preserves relationships)
• Financial data → kept as-is (AI needs amounts for tax calculations)
• State abbreviations → kept as-is (needed for state tax determination)

Layer 3: Encrypted Vault

• Token ↔ PII mappings stored in Fernet-encrypted local files
• Encryption: AES-128-CBC + HMAC-SHA256
• Key derivation: PBKDF2 with 600,000 iterations (OWASP recommended minimum)
• Each processing session gets its own vault file
• Secure deletion: vault files are overwritten with random data before deletion

Layer 4: Pre-Send Safety Check

• Last-resort regex scan for SSN patterns (XXX-XX-XXXX) in the text about to be sent
• If any SSN is detected in the "redacted" text, the API call is blocked with an error
• This catches edge cases where detection might have missed something

Layer 5: Comprehensive Test Suite

• 152 tests including dedicated PII leak prevention tests
• Tests process mock W-2s, 1099s, multi-page documents, and dense PII documents
• Each test verifies that no known PII value appears in the redacted output
• Mocked Claude API tests capture the exact payload and assert zero PII
• Image-based (scanned) PDF and phone photo (PNG/JPG) tests

What CipherTax Does NOT Protect Against

We believe in transparency about limitations:

• No automated system guarantees 100% PII detection. Unusual PII formats, misspelled names, or PII embedded in unusual contexts may be missed. Always review the redacted output before sending.
• Financial data is intentionally NOT redacted. Income amounts, tax figures, and state abbreviations are sent to the AI because it needs them for calculations.
• The Anthropic API key is stored locally. Protect your .env file.
• CipherTax is not tax advice software. The tax calculator is for estimation. Consult a CPA for filing.

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Tax Data Sensitivity Levels (DSL)

CipherTax classifies every piece of tax data by sensitivity level, adapted from enterprise data security frameworks. This classification drives all redaction decisions — it's not guesswork, it's a formal policy.

DSL	Level	Description	CipherTax Action	Risk if Exposed
1	🟢 PUBLIC	Data with no privacy risk	✅ Send to AI as-is	None
2	🔵 INTERNAL	De-identified financial data	✅ Send to AI as-is	Low — no identity context
3	🟡 CONFIDENTIAL	Personal identifiers	🔒 Redact → token	Identity correlation
4	🔴 RESTRICTED	Government IDs, bank accounts	🔐 Redact + AES encrypt	Identity theft, financial fraud
5	⛔ CRITICAL	Filing credentials, legal authority	⛔ Never store or transmit	Catastrophic — full account takeover

DSL 1 — PUBLIC (Safe to share)

Data	Examples	IRS Form Fields
Tax year	2024	1040 header
Form type	W-2, 1099-INT, Schedule C	All form headers
Filing status	Single, MFJ, HoH	1040 lines 1-5
Number of dependents	2, 0	1040 line 6d

DSL 2 — INTERNAL (Financial data — safe for AI)

Data	Examples	Why AI Needs It
Income amounts	$75,000, $1,245.67	Tax bracket calculation
Tax withheld	$12,000, $5,100	Refund/owed computation
Deduction amounts	$14,000 mortgage interest	Itemized vs standard comparison
State abbreviation	CA, IL, TX	State tax determination
Business expenses	Advertising: $5,000	Schedule C calculation

Key insight: These amounts are NOT personally identifying without the identity data from DSL 3-4. The number "$75,000" doesn't tell you who earned it.

DSL 3 — CONFIDENTIAL (Personal identifiers — REDACT)

Data	Examples	Redaction	Risk
Person name	John Smith, Maria Rodriguez	→ [PERSON_1]	Identity correlation
Email address	[e-mail]	→ [EMAIL_1]	Phishing, spam
Phone number	[phone]	→ [PHONE_1]	Social engineering, SIM swap
Street address	742 Evergreen Terrace	→ [ADDRESS_1]	Physical location exposure
Date of birth	03/15/1985	→ [DATE_1]	Identity verification factor
Employer name	Acme Corp, Google LLC	→ [ORGANIZATION_1]	Employment verification

DSL 4 — RESTRICTED (Government IDs & bank info — REDACT + ENCRYPT)

Data	Examples	Redaction	Risk
SSN	123-45-6789	→ [SSN_1] + AES vault	Identity theft, fraudulent tax filing, credit fraud
EIN	12-3456789	→ [EIN_1] + AES vault	Business identity fraud
ITIN	912-34-5678	→ [ITIN_1] + AES vault	Tax identity theft
Bank account	1234567890	→ [BANK_ACCT_1] + AES vault	Unauthorized bank transactions
Routing number	021000021	→ [ROUTING_1] + AES vault	ACH fraud
W-2 control number	A1B2C3D4E5	→ [CONTROL_NUM_1] + AES vault	W-2 forgery

These are stored only in the locally encrypted vault (Fernet/AES-128-CBC + HMAC-SHA256, PBKDF2 with 600,000 iterations). The vault file is overwritten with random data before deletion.

DSL 5 — CRITICAL (Never store or transmit)

Data	Risk	CipherTax Policy
IRS e-File PIN / IP PIN	Enables fraudulent tax return filing	⛔ Never stored — user warned if detected
Tax portal credentials	Full account takeover	⛔ Never stored — not processed
Power of Attorney (Form 2848)	Legal authority over tax matters	⛔ Never stored — flagged for manual review

If CipherTax detects DSL 5 data in your documents, it will warn you and refuse to process it. These credentials should be entered directly into IRS systems, never shared with any third party including AI.

How DSL Drives Redaction

from ciphertax.tax.data_sensitivity import get_fields_safe_for_ai, get_fields_to_redact

# What's safe to send to Claude?
for field in get_fields_safe_for_ai():
    print(f"✅ {field.field_name} (DSL {field.dsl})")

# What must be redacted?
for field in get_fields_to_redact():
    print(f"🔒 {field.field_name} (DSL {field.dsl}) → {field.ai_action}")

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Tax Calculation Engine

CipherTax includes a complete federal tax calculator for tax year 2024 that follows the IRS Form 1040 flow:

Example Output: Single W-2 Employee ($75,000)

  Filing Status:          Single
  Total Wages:            $   75,000.00
  Gross Income:           $   75,000.00
  Adjustments:            $    1,800.00    (student loan interest)
  AGI:                    $   73,200.00
  Deduction (standard):  $   14,600.00
  Taxable Income:         $   58,600.00

  Ordinary Tax:           $    7,945.00    (10% + 12% + 22% brackets)
  ─────────────────────────────────────
  TOTAL TAX:              $    7,945.00

  Federal Withholding:    $   10,500.00
  ✅ REFUND:              $    2,555.00

  Effective Tax Rate:           10.6%
  Marginal Tax Rate:              22%

Example: Complex Scenario (MFJ, W-2 + Freelance + Investments + Rental)

  Income Summary:
  W-2 Wages:              $  135,000.00
  Self-Employment:        $   35,000.00
  Interest:               $    2,200.00
  Dividends:              $    4,500.00
  Capital Gains:          $    9,200.00
  Rental Income:          $    3,220.00
  GROSS INCOME:           $  189,120.00

  Deduction (itemized):   $   31,000.00
  QBI Deduction:          $    7,000.00
  TAXABLE INCOME:         $  148,157.33

  Ordinary Tax:           $   20,940.61
  Capital Gains Tax:      $    1,200.00
  Child Tax Credit:      -$    4,000.00    (2 children)
  Self-Employment Tax:    $    4,945.34
  TOTAL TAX:              $   23,085.95

  Withholding + Est:      $   30,000.00
  ✅ REFUND:              $    6,914.05    Effective: 12.2%

What the Calculator Handles

Feature	Details
Tax Brackets	All 7 marginal rates (10%–37%) × 4 filing statuses
Standard Deduction	Including age 65+ and blindness additions
Itemized Deductions	SALT cap ($10K), medical (7.5% AGI floor), mortgage interest, charitable
Capital Gains	Short-term (ordinary rates) + long-term (0%/15%/20%)
Self-Employment Tax	Schedule SE: 15.3% (SS + Medicare) on 92.35% of net income
QBI Deduction	Section 199A: 20% deduction with income phaseout
Child Tax Credit	$2,000/child with phaseout above $200K/$400K
NIIT	3.8% Net Investment Income Tax above $200K/$250K
Additional Medicare	0.9% above $200K/$250K
Retirement	IRA deduction phaseouts, 401(k) limits

Tax Optimization Suggestions

After computing your tax, CipherTax analyzes your return and suggests:

  1. [HIGH] Maximize 401(k) contributions
     You contributed $6,000. The limit is $23,000 — you have $17,000 of room.
     💰 Potential savings: $3,740

  2. [HIGH] Open a SEP-IRA for self-employment income
     You can contribute up to $7,000 to a SEP-IRA.
     💰 Potential savings: $1,540

  3. [MEDIUM] Consider tax-loss harvesting
     You have net capital gains of $9,200. Selling losers can offset gains.
     💰 Potential savings: $1,380

  4. [MEDIUM] Consider an HSA contribution
     Triple tax advantage: deductible, tax-free growth, tax-free withdrawals.
     💰 Potential savings: $913

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How to Use the Output

1. Review the Redacted Text

Before CipherTax sends anything to AI, review what will be sent:

ciphertax inspect w2.pdf    # Dry run — shows redacted text, nothing sent

2. Process Your Documents

ciphertax process w2.pdf --task extract     # Extract structured data
ciphertax process w2.pdf --task advise -q "Am I eligible for EITC?"
ciphertax process w2.pdf 1099-int.pdf --task file   # Filing preparation

3. Understand AI Responses

Claude's response uses the same tokens. CipherTax automatically restores your real PII:

What Claude says: "[PERSON_1] earned $92,450.00 at [ORGANIZATION_7] (EIN [EIN_1])"

What you see (after rehydration): "Maria Elena Rodriguez earned $92,450.00 at Acme Technology Solutions Inc (EIN 45-6789012)"

4. Use Tax Calculations

from ciphertax.tax.calculator import TaxCalculator
from ciphertax.tax.forms import FilingStatus, TaxInput, W2Income

calc = TaxCalculator(tax_year=2024)
result = calc.compute(TaxInput(
    filing_status=FilingStatus.SINGLE,
    w2s=[W2Income(wages=75_000, federal_tax_withheld=10_500)],
))

print(f"Tax: ${result.total_tax:,.2f}")
print(f"Refund: ${result.refund:,.2f}")
print(f"Effective rate: {result.effective_tax_rate:.1%}")

5. Before Filing

• ✅ Review the AI's output for accuracy
• ✅ Cross-check tax calculations against your expectations
• ✅ Verify all income sources are included
• ✅ Consider the optimization suggestions
• ⚠️ Consult a qualified tax professional — CipherTax provides estimates, not tax advice
• 📝 Use the structured data to fill out your actual tax forms or input into tax filing software

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Installation

Prerequisites

• Python 3.10+
• Tesseract OCR (for scanned PDFs and photos)

# macOS
brew install tesseract

# Ubuntu/Debian
sudo apt-get install tesseract-ocr

# Windows — download from https://github.com/UB-Mannheim/tesseract/wiki

Install

git clone https://github.com/z26zheng/CipherTax.git
cd CipherTax

python -m venv .venv
source .venv/bin/activate    # macOS/Linux

pip install -e ".[dev]"
python -m spacy download en_core_web_sm

cp .env.example .env
# Edit .env → add your ANTHROPIC_API_KEY

Run the Demo

python examples/demo_tax_filing.py

This runs 4 scenarios end-to-end: simple W-2 filing, complex multi-income filing, PII redaction pipeline, and CPA questionnaire.

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Supported Input Formats

Format	Type	Support
Digital PDF	Text-selectable PDFs	✅ PyMuPDF extraction
Scanned PDF	Image-based PDFs	✅ Tesseract OCR
PNG images	Phone photos	✅ Direct OCR
JPG/JPEG images	Phone photos	✅ Direct OCR
TIFF images	Scanner output	✅ Direct OCR
BMP, WebP	Other image formats	✅ Direct OCR

Supported Tax Forms

Form	Description
W-2	Wage and Tax Statement
1099-INT	Interest Income
1099-DIV	Dividends (qualified + ordinary)
1099-NEC	Nonemployee Compensation
1099-B	Brokerage Proceeds (stocks, crypto)
1099-R	Retirement Distributions
K-1	Partnership / S-Corp Income
SSA-1099	Social Security Benefits
Schedule C	Business Profit/Loss
Schedule E	Rental Income
1040	Individual Income Tax Return

PII Entities Detected

Entity	Detection Method	Example	Action
SSN	Custom regex + validation	123-45-6789	🔴 Always redact
EIN	Custom regex + context	98-7654321	🔴 Always redact
ITIN	Custom regex	912-34-5678	🔴 Always redact
Person names	spaCy NER	John Smith	🔴 Always redact
Email	Presidio built-in	[e-mail]	🔴 Always redact
Phone	Presidio built-in	[phone]	🔴 Always redact
Bank account	Custom + context	12345678901	🔴 Always redact
Routing number	Custom + context	021000021	🔴 Always redact
Addresses	spaCy NER	123 Main St	🔴 Always redact
Income amounts	—	$75,000	🟢 Kept for tax math
State	—	CA, IL, TX	🟢 Kept for state tax
Filing status	—	Single, MFJ	🟢 Kept for calculations

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Tests

152 tests covering:

Category	Count	What's Tested
PII Detection	10	SSN, EIN, names, emails, phones, overlap resolution
Tokenization	9	Redaction, consistency, roundtrip, normalization
Rehydration	7	Token restoration, unknown tokens, formatting
Vault	12	Encryption, load/store, wrong password, secure delete
PII Leak Prevention	29	No SSN/name/EIN/email/phone in redacted output across all form types
Pipeline	22	End-to-end, multi-doc, scanned PDF, images, Claude mock
Edge Cases	26	Empty PDF, Unicode, duplicate PII, ZIP codes, file routing
Tax Calculator	37	Brackets, SE tax, QBI, credits, optimizer, questionnaire

pytest                    # Run all 152 tests
pytest -v                 # Verbose output
pytest --cov=ciphertax    # With coverage report

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Project Structure

CipherTax/
├── src/ciphertax/
│   ├── extraction/          # PDF + image text extraction (PyMuPDF, Tesseract)
│   ├── detection/           # PII detection (Presidio + custom tax recognizers)
│   ├── redaction/           # Tokenizer (PII → tokens) + Rehydrator (tokens → PII)
│   ├── vault/               # Encrypted local storage (Fernet/AES-256)
│   ├── ai/                  # Claude API client (sends only redacted text)
│   ├── tax/                 # Tax calculation engine
│   │   ├── data/            # Federal tax constants by year
│   │   ├── calculator.py    # Full 1040 computation
│   │   ├── forms.py         # Data models for all tax forms
│   │   ├── questionnaire.py # CPA-style intake
│   │   └── optimizer.py     # Tax optimization suggestions
│   ├── pipeline.py          # Orchestrates the full workflow
│   └── cli.py               # Command-line interface
├── examples/
│   └── demo_tax_filing.py   # End-to-end demo with 4 scenarios
├── tests/                   # 152 tests (pytest)
├── pyproject.toml
└── README.md

Contributing

Contributions welcome! Areas that need help:

• State tax support — Currently federal-only
• Tax year 2025 data — Adding new year's brackets and limits
• Additional form recognizers — Better detection for specific form layouts
• UI/Web interface — Currently CLI + Python API only

License

MIT — see LICENSE for details.

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⚠️ Disclaimer

CipherTax is a privacy tool and tax estimation tool, not a certified tax preparation product.

• PII detection is not guaranteed to be 100% complete. Always review the redacted output before sending to any AI service. Unusual formats or embedded PII may not be detected.
• Tax calculations are estimates based on 2024 IRS data. They do not account for every edge case, state taxes, or AMT in all scenarios.
• This is not tax advice. Consult a qualified tax professional (CPA or Enrolled Agent) before filing your return.
• You are responsible for reviewing all output and ensuring accuracy before filing.