Cost basis via API - Anchorage Digital

When assets are deposited from an external source, Anchorage may not have the original acquisition details. If cost basis isn’t provided, the system defaults to $0, which may affect your reported gains/losses. This information ensures that tax lots and gains/loss calculations reflect accurate historical cost basis. Cost basis information you provide may impact data reported on 1099-DA, for eligible US tax-paying entities. Anchorage Digital partners with a third-party tax reporting provider to support tax reporting, including 1099-DA, 1099-MISC, and 1099-INT.

Anchorage Digital does not provide financial, tax, or legal advice. Consult a qualified professional for guidance specific to your situation.

Cost basis method (HIFO)

Anchorage Digital uses HIFO (Highest-In, First-Out) by default for cost basis accounting unless otherwise configured. Example (HIFO):

Purchase	Quantity	Price
Purchase 1	10 BTC	$20,000/BTC
Purchase 2	20 BTC	$22,000/BTC
Purchase 3	15 BTC	$35,000/BTC

If 25 BTC are sold, HIFO assumes:

15 BTC from Purchase 3 sold first (highest cost)
Remaining 10 BTC from Purchase 2

Our tax reporting provider offers HIFO, LIFO, and FIFO. Contact Anchorage customer service to request a change in default cost basis methodology. Individual lot selection is not currently available.

Default logic and validations

If a deposit is missing user-provided cost basis, the system assigns a default of 0. Provide cost basis promptly after deposits complete to avoid inaccurate reporting.
Cost basis updates support up to 100 lots per transaction.
The acquisition date must be on or before the transfer/deposit date.
Trades may have small rounding differences due to settlement precision. Your internal reconciliation should account for this.

API workflow

List tax accounts

Identify tax accounts your API credentials can access.GET /tax/accounts

{
  "accounts": [
    {
      "taxAccountId": "acc_123",
      "name": "Example 123"
    }
  ]
}

List deposit transactions for a tax account

Retrieve deposit transactions for a given tax account. Filter by hasCostBasis=false to return only deposits missing user-provided cost basis.GET /tax/accounts/{taxAccountId}/transactions

{
  "data": [
    {
      "assetType": "BTC",
      "externalId": "9be748be-d760-4d36-90f8-86b699c4e8bd",
      "id": "9cd9f4d4-078b-4e44-a308-7662fec0f546",
      "receivedAssets": [
        {
          "acquisitionDatetime": "2026-04-06T17:55:48.083Z",
          "costBasis": "2500",
          "quantity": "1.0"
        }
      ],
      "transactionTime": "2022-07-30T22:15:31.99999Z"
    }
  ],
  "page": {
    "next": "<next page url>"
  }
}

Provide cost basis for a deposit transaction

Submit one or more lots whose total quantity matches the deposit quantity.PATCH /tax/accounts/{taxAccountId}/transactions/{transactionId}

{
  "lots": [
    {
      "quantity": "0.7500",
      "costBasis": "15000.00",
      "acquisitionDate": "2024-05-10T14:19:52.539Z"
    },
    {
      "quantity": "0.5000",
      "costBasis": "12000.00",
      "acquisitionDate": "2023-11-02T14:19:52.539Z"
    }
  ]
}

Validation rules:

Total lot quantities must equal the transaction quantity
Acquisition date must be on or before transfer date
Maximum 100 lots per transaction

Confirm the update

Re-fetch the transaction and verify costBasis is no longer 0 and lots were accepted as submitted.

Operational guidance

Timing: Update cost basis as soon as possible after an in-kind deposit so downstream reporting reflects accurate lots and gains/loss.
Source of truth: Use your internal records (exchange statements, wallet history, or prior custodians’ reports) to determine acquisition dates and basis.
Auditability: Retain supporting documentation for the lot inputs used.

Troubleshooting

Common causes of failures:

Issue	Cause
Request rejected	Lot quantities don’t sum to deposit quantity
Date error	Acquisition date is after the transfer date
Too many lots	More than 100 lots submitted
Asset mismatch	Lots don’t match deposit asset type
Unknown asset	Asset type not recognized

Tax terminology

Term	Overview
Tax account	Top-level unit used in the API for tax reporting
Tax transaction	A tax-relevant event such as a deposit
Gains/loss	Difference between sale price and cost basis
Inventory	Total quantity and cost basis of a specific asset type, consisting of multiple tax lots
Tax lot	A specific group of units acquired at the same time and cost basis
Acquisition date	Date when an individual gains control of an asset
Cost basis	Value of an asset in USD at time of acquisition, used to calculate gains or losses
Cost basis method	Methodology used to compute gains/losses (e.g., HIFO, FIFO, LIFO)
Missing cost basis	Occurs when assets are transferred into Anchorage without original acquisition details
Holding period	Duration an asset is held before being sold
Realized gain/loss	Gains or losses from the sale or disposition of an asset
Unrealized gain/loss	Gains or losses from price fluctuation not yet realized through a sale

​Cost basis method (HIFO)

​Default logic and validations

​API workflow

​Operational guidance

​Troubleshooting

​Tax terminology

Cost basis method (HIFO)

Default logic and validations

API workflow

Operational guidance

Troubleshooting

Tax terminology