Crypto/stock cost basis (FIFO/LIFO/HIFO) API

Compute cost basis and realized gain for a disposal using FIFO, LIFO, or HIFO lot matching across your purchase lots, returning proceeds, matched-lot basis, realized gain, gain per unit, and the matched lots. Lot-accounting math LLMs get wrong. Answers 'FIFO cost basis for selling 15 of 20 coins','HIFO to minimize my gain','realized gain on this stock sale','LIFO vs FIFO basis'.

Price$0.01per request

MethodPOST

Route/v1/calc/tax-crypto-cost-basis

StatusLive

MIME typeapplication/json

Rate limit120/minute

CacheNo cache

taxcost-basisfifolifohifocryptocapital-gainscalc

API URLhttps://x402.hexl.dev/v1/calc/tax-crypto-cost-basis

Integration docs

Example request

{
  "lots": [
    {
      "quantity": 10,
      "price": 100
    },
    {
      "quantity": 10,
      "price": 200
    }
  ],
  "sellQuantity": 15,
  "sellPrice": 250,
  "method": "FIFO"
}

Example response

{
  "method": "FIFO",
  "sellQuantity": 15,
  "sellPrice": 250,
  "proceeds": 3750,
  "costBasis": 2000,
  "realizedGain": 1750,
  "gainPerUnit": 116.6667,
  "isGain": true,
  "lotsMatched": [
    {
      "quantity": 10,
      "price": 100,
      "cost": 1000
    },
    {
      "quantity": 5,
      "price": 200,
      "cost": 1000
    }
  ],
  "note": "Estimate. Lot matching only; does not classify short/long-term (use tax-capital-gains) or apply wash-sale."
}

Input schema

{
  "type": "object",
  "required": [
    "lots",
    "sellQuantity",
    "sellPrice"
  ],
  "properties": {
    "lots": {
      "type": "array",
      "description": "Purchase lots",
      "items": {
        "type": "object",
        "properties": {
          "quantity": {
            "type": "number"
          },
          "price": {
            "type": "number"
          },
          "date": {
            "type": "string"
          }
        }
      },
      "examples": [
        [
          {
            "quantity": 10,
            "price": 100
          },
          {
            "quantity": 10,
            "price": 200
          }
        ]
      ]
    },
    "sellQuantity": {
      "type": "number",
      "examples": [
        15
      ]
    },
    "sellPrice": {
      "type": "number",
      "examples": [
        250
      ]
    },
    "method": {
      "type": "string",
      "enum": [
        "FIFO",
        "LIFO",
        "HIFO"
      ],
      "examples": [
        "FIFO"
      ]
    }
  }
}

Output schema

{
  "type": "object",
  "additionalProperties": true
}