Cost Basis Methods

Supported methods

Method	ID	Country	Notes
First In, First Out	FIFO	🌍	Oldest lots sold first (IRS default)
Last In, First Out	LIFO	🌍	Must elect Specific ID (IRS)
Highest In, First Out	HIFO	🌍	Must elect Specific ID (IRS)
Specific ID	SPECIFIC_ID	🌍	Manual lot selection
Germany FIFO	GERMANY_FIFO	🇩🇪	§23 EStG, 1-year holding exemption
PMPA	PMPA	🇫🇷	Plus-value mobilière, weighted average
Total Average	TOTAL_AVERAGE	🌍	Average cost basis
UK Share Pooling	UK_SHARE_POOLING	🇬🇧	Section 104 pool + 30-day rule
AU CGT Discount	AU_CGT_DISCOUNT	🇦🇺	FIFO + 50% discount on long-term gains (ATO s.115)
CA ACB	CA_ACB	🇨🇦	Weighted average Adjusted Cost Base (CRA IT-387R2)
KR Virtual Asset	KR_VIRTUAL_ASSET	🇰🇷	FIFO; 22% flat rate + KRW 2.5M exemption at report layer
IN VDA	IN_VDA	🇮🇳	FIFO; losses not deductible (s.115BBH)
ES CGT	ES_CGT	🇪🇸	FIFO; tiered 19–27% rates at report layer

IRS note

The IRS allows FIFO and Specific Identification for crypto (Rev. Rul. 2023-14). LIFO and HIFO are technically Specific ID strategies — you must maintain lot-level records and consistently apply your method.

Usage

import { computeGains, compareAllMethods } from '@dtax/tax-engine';

// Single method
const result = computeGains(transactions, {
  method: 'FIFO',
  taxYear: 2024,
});

// Compare all comparable methods (excludes SPECIFIC_ID)
const comparison = compareAllMethods(transactions, 2024);
comparison.forEach(({ method, totalGain, recommendation }) => {
  console.log(`${method}: $${totalGain} ${recommendation ? '← recommended' : ''}`);
});

Result shape

interface GainResult {
  shortTermGain: number;
  longTermGain: number;
  totalGain: number;
  disposals: Disposal[];
  unrealizedGain?: number;
}