coinbasis

A pure-Python, stdlib-only crypto tax-lot cost-basis accounting engine.

I built this library to provide a correct, dependency-free accounting engine in Python: eight transaction event types, five cost-basis methods, IRS gift dual-basis rules, per-wallet lot pools, and progressive tax-bracket estimation — all without a single runtime dependency and with Decimal arithmetic throughout for exact decimal precision.

Features

• Five cost-basis methods: FIFO, LIFO, HIFO, Average Cost, Specific ID
• Eight transaction types: Buy, Sell, Trade, Income, Spend, Transfer, GiftSent, GiftReceived
• Per-wallet lot pooling: disposals draw only from the named wallet; transfers move lots between wallets preserving original basis and holding-period clock
• IRS gift dual-basis rule: GiftReceived lots carry donor basis and FMV; the engine applies the correct gain/loss/dead-zone calculation at disposal time
• Short/long-term classification: strict > 365 days boundary
• Tax-year reports: CapitalGainsReport (Form 8949-shaped), IncomeReport, PortfolioReport with unrealized P&L and allocation percentages
• Progressive tax estimation: configurable brackets + short-term flat rate; US preset included via TaxConfig.default()
• Portfolio statistics: period returns, volatility, Sharpe ratio, max drawdown, cumulative return
• JSON round-trip: externally-tagged JSON schema ({"Buy": {...}}); Decimal values serialized as strings for unambiguous round-trip
• Zero runtime dependencies: stdlib only (decimal, dataclasses, datetime, json, enum, math)

Install

pip install coinbasis

Quickstart

from decimal import Decimal
from datetime import datetime, timezone
from coinbasis import Portfolio, CostBasisMethod, Buy, Sell

def dt(y, m, d):
    return datetime(y, m, d, tzinfo=timezone.utc)

txs = [
    Buy(timestamp=dt(2020, 1, 1), wallet="hot", asset="btc",
        quantity=Decimal("1"), unit_price=Decimal("100"), fee=Decimal("0")),
    Buy(timestamp=dt(2021, 1, 1), wallet="hot", asset="btc",
        quantity=Decimal("1"), unit_price=Decimal("300"), fee=Decimal("0")),
    Sell(timestamp=dt(2022, 1, 1), wallet="hot", asset="btc",
         quantity=Decimal("1"), unit_price=Decimal("500"), fee=Decimal("0")),
]

p = Portfolio.from_transactions(txs)

# FIFO: matches oldest lot first -> gain 400
fifo_gain = sum(g.gain for g in p.realized_gains(CostBasisMethod.FIFO))
print(fifo_gain)       # Decimal('400')

# HIFO: matches highest-cost lot first -> gain 200
hifo_gain = sum(g.gain for g in p.realized_gains(CostBasisMethod.HIFO))
print(hifo_gain)       # Decimal('200')

# Tax-year capital gains report
report = p.capital_gains_report(CostBasisMethod.FIFO, tax_year=2022)
print(report.long_term_gain)   # Decimal('400')
print(report.short_term_gain)  # Decimal('0')

Income and portfolio valuation

from coinbasis import Income, IncomeSource, Transfer
from coinbasis.tax import TaxConfig

# Staking income creates a lot at its FMV and records an IncomeEvent
txs = [
    Income(timestamp=dt(2021, 1, 1), wallet="hot", asset="eth",
           quantity=Decimal("2"), value=Decimal("200"), source=IncomeSource.STAKING),
]
p = Portfolio.from_transactions(txs)
print(p.income_report(2021).total_income)  # Decimal('200')

# Valuation against live prices
report = p.valuation(CostBasisMethod.FIFO, {"eth": Decimal("150")})
print(report.total_unrealized)  # Decimal('100')

# Tax estimate
from coinbasis.tax import estimate, TaxConfig
est = estimate(short_gain=Decimal("10000"), long_gain=Decimal("50000"),
               config=TaxConfig.default())
print(est.total_tax)

JSON round-trip

from coinbasis.serialization import ledger_to_json, ledger_from_json

json_str = ledger_to_json(txs, indent=2)
restored = ledger_from_json(json_str)

Examples

Runnable scripts live in examples/. Each is self-contained and offline (coinbasis has no network dependency) and prints clearly labeled output. Run any of them with python examples/<name>.py.

Development

git clone https://github.com/Technical-1/coinbasis-py
cd coinbasis-py
pip install -e ".[dev]"
python3 -m pytest          # run full test suite
python3 -m ruff check src/ # lint
python3 -m build           # build sdist + wheel

Project Structure

src/coinbasis/
  __init__.py      Public API surface — all re-exports
  errors.py        PortfolioError exception hierarchy (8 typed errors)
  transaction.py   Transaction (8 frozen dataclass variants) + IncomeSource
  method.py        CostBasisMethod enum, LotPick, LotSelection, order_for()
  lot.py           Internal Lot + GiftBasis dataclasses
  engine.py        Internal ledger-replay engine (_Engine, run())
  report.py        Term, RealizedGain, IncomeEvent, Holding, PortfolioReport, ...
  portfolio.py     Portfolio facade — public query methods
  tax.py           TaxBracket, TaxConfig, TaxEstimate, estimate()
  stats.py         returns_from_values, volatility, sharpe_ratio, max_drawdown, cumulative_return
  serialization.py JSON (de)serialization — externally-tagged transaction schema

tests/
  test_engine.py         Engine unit tests
  test_end_to_end.py     End-to-end numeric checks over representative ledgers
  test_portfolio.py      Portfolio facade tests
  test_serialization.py  JSON round-trip tests
  test_stats.py          Statistics module tests
  test_tax.py            Tax estimation tests
  test_properties.py     Property-based invariant tests
  (+ more)

Not tax advice

This library computes cost-basis and gain estimates based on the inputs you provide. Consult a qualified tax professional for advice specific to your situation.

License

MIT OR Apache-2.0

Author

Jacob Kanfer — GitHub: Technical-1