Tax data - Anchorage Digital

Topics covered:

Tax data overview and accounting method
Critical transaction and cost basis considerations
Supported tax forms
Integration steps

Anchorage Digital does not provide financial, tax, or legal advice.

Tax data overview

Anchorage Digital reports tax data for two account types:

Taxable accounts — individual, trust, joint, etc.
Individual Retirement Accounts (IRA)

HIFO accounting method

Anchorage Digital uses HIFO (highest-in, first-out) by default — the highest-priced units are sold first when calculating cost basis. This can be changed at the wealth manager level or overridden per account. Example: Investor holds 10 BTC at

20k, 20 BTC at

22k, 15 BTC at $35k. Selling 25 BTC under HIFO:

15 BTC from the $35k purchase sold first
10 BTC from the $22k purchase sold next

Tax reporting partnership

Anchorage Digital partners with a third-party tax reporting provider to give wealth managers and end clients required tax data, compliance features, and tax forms.

Transaction types

Type	Description
On-chain transactions	Asset movement on-chain. Not relevant to tax APIs.
Subaccount transactions	Asset movement on the wealth manager’s ledger at Anchorage Digital.
Tax transactions	Any transaction with a taxable event — these are the transactions in the tax API.

Taxable subaccount transaction event types: DEPOSIT, TRADE, WITHDRAW.

Cost basis tracking

Cost basis is tracked automatically throughout the asset lifecycle. For in-kind deposits, the wealth manager and end client must supply the cost basis via API.

`subaccountId` and `customerId` mapping

Each subaccountId maps 1:1 to an Account Owner ID with our tax reporting provider (which Anchorage Digital maps to customerId). This provides:

Accurate, segregated tracking — clear traceability between strategies, trades, and their cost-basis impact.
Tax-loss harvesting flexibility — losses can be realized within individual accounts without affecting others.

Tax terminology

Term	Description
Tax transaction	Data used by our tax reporting provider to generate tax outputs. Differs from subaccount or on-chain transactions.
Gain/loss	Difference between sale price and cost basis. Reported as `SHORT_TERM` or `LONG_TERM` by tax year.
Inventory	Total quantity and cost basis of a specific asset type held by a subaccount, comprised of multiple tax lots.
Tax lot	A group of units acquired at the same time and cost basis.
Acquisition date	Date an individual gains control of an asset. Determines long-term vs. short-term holding period in the US.
Cost basis	Value of an asset at acquisition time; used to calculate gain/loss on disposal.
Cost basis method	HIFO (default) or LIFO/FIFO (configurable). Individual lot selection is on the roadmap.
Missing cost basis	Occurs when transferring assets in-kind into a deposit wallet. Can be supplied via API.
Holding period	Duration an asset is held. Long-term (>1 year) receives preferential US tax treatment.
Realized gain/loss	Gains/losses from actual sale or disposition of an asset.
Unrealized gain/loss	Gains/losses from price fluctuation without disposal.

Critical considerations

Missing cost basis is null, not 0.
Default method is HIFO — configurable per wealth manager or per account.
All tax data is at the subaccount level, regardless of account owners.
Trade rounding (dust): Trades cannot always settle to full decimal precision. Rounded values are stored in the ledger and used for balancing, but full-precision quantities appear in trade confirmations and tax reporting — meaning tax data and ledger values may differ slightly by a small “dust” amount. This is an industry-wide issue with trade confirms vs. custody precision.

Supported tax forms

Anchorage Digital does not perform tax reporting on behalf of wealth managers or end clients, and does not issue tax forms directly. Our tax reporting provider generates and provides forms based on the data Anchorage Digital provides.

Account type	Form	Description	Deadline	Status
Taxable	Cost-basis data	Proceeds and cost basis per transaction for Form 8949 and Schedule D.	Preferred by Feb 15
Taxable	1099-B	Proceeds from brokerage/trading transactions.	Jan 31
Taxable	1099-MISC	Miscellaneous income (staking rewards, services, mining).	Jan 31	Coming soon
Non-taxable	1099-R	Distributions from retirement accounts.	Jan 31	Coming soon
Non-taxable	Form 5498	IRA contribution reporting.	June 2	Coming soon

Integration steps

Sandbox tax testing may be limited due to the absence of a full trade → settlement lifecycle for mainnet assets.

Step 1: Review tax transactions

GET /v2/tax/transactions/{subaccountId} Returns tax transaction data for a subaccount. Check for missing cost basis on deposits.

curl --request GET \
     --url https://api.anchorage-staging.com/v2/tax/transactions/{subaccountId} \
     --header 'Api-Access-Key: {API Key}' \
     --header 'accept: application/json'

{
  "data": [
    {
      "externalId": "dad566f7-d5e6-4bbf-a2ef-c092435163f9",
      "fee": { "assetType": "ETH", "costBasis": "3335.22", "quantity": "0.029983029605243432217" },
      "feeAsset": [{ "assetType": "ETH", "costBasis": "3335.22", "quantity": "0.029983029605243432217" }],
      "id": "6159224d-db88-47a4-99ae-1e3b8aeed671",
      "received": { "assetType": "ETH", "costBasis": "3335.22", "quantity": "29.983029605243432217" },
      "receivedAsset": [{ "assetType": "ETH", "costBasis": "3335.22", "quantity": "29.983029605243432217" }],
      "sent": { "assetType": "USD", "costBasis": "1", "quantity": "100000" },
      "sentAsset": [{ "assetType": "USD", "costBasis": "1", "quantity": "100000" }],
      "transactionTime": "2024-03-22T17:48:57.237Z",
      "type": "TRADE"
    }
  ]
}

Step 2: Update missing cost basis

PATCH /v2/tax/transaction/{transactionId} Only cost basis data can be updated. Transaction asset and quantity cannot be changed.

curl --request PATCH \
     --url https://api.anchorage-staging.com/v2/tax/transaction/{transactionId} \
     --header 'accept: application/json' \
     --header 'content-type: application/json' \
     --data '{
  "type": "DEPOSIT",
  "assetType": "BTC",
  "lots": [
    {
      "acquisitionDatetime": "2025-03-03T14:48:06.111Z",
      "quantity": "1.0",
      "cost": "2500"
    }
  ],
  "acquisitionDatetime": "2025-03-03T14:48:06.111Z",
  "data": {
    "assetType": "BTC",
    "costBasis": "2500",
    "quantity": "1.0"
  }
}'

{
  "data": {
    "transactionId": "9cd9f4d4-078b-4e44-a308-7662fec0f546"
  }
}

Step 3: View asset inventory

GET /v2/tax/inventory/{subaccountId}/{assetType} Returns total quantity and all tax lots for a specific asset in a subaccount.

curl --request GET \
     --url https://api.anchorage-staging.com/v2/tax/inventory/{subaccountId}/LDO \
     --header 'Api-Access-Key: {API Key}' \
     --header 'accept: application/json'

{
  "data": {
    "summary": {
      "AverageUnitCost": "1.633895117039317318810783072486812",
      "assetType": "LDO",
      "costBasis": "46.8803541265509",
      "lots": [
        { "acquisitionDatetime": "2025-01-21T15:28:17.611Z", "cost": "5.0", "id": "164963b5-0bbd-505b-91c0-dbe8e309c900", "quantity": "2.646830567706262384", "unitCost": "1.889051781781781798" },
        { "acquisitionDatetime": "2025-01-21T15:20:31.747Z", "cost": "1.87858968297", "id": "ee406c6f-a955-50bc-92bb-aee73bcd7ae5", "quantity": "1", "unitCost": "1.87858968297" }
      ],
      "quantity": "28.692388904068676642",
      "totalQuantityMissingCostBasis": "0",
      "totalQuantityWithCostBasis": "28.692388904068676642"
    }
  }
}

GET /v2/tax/inventory/summary/{subaccountId} Returns inventory summary across all assets.

curl --request GET \
     --url https://api.anchorage-staging.com/v2/tax/inventory/summary/{subaccountId} \
     --header 'Api-Access-Key: {API Key}' \
     --header 'accept: application/json'

{
  "data": [
    { "assetType": "SOL", "costBasis": "10.002517283800791293", "quantity": "0.048968461518597327", "quantityWithCostBasis": "0.048968461518597327", "quantityWithoutCostBasis": "0" },
    { "assetType": "ETH", "costBasis": "29.999999999999999002", "quantity": "0.012590000901477938", "quantityWithCostBasis": "0.010911660562946608", "quantityWithoutCostBasis": "0.00167834033853133" }
  ]
}

Step 4: Review cost basis and gains

GET /v2/tax/gains/summary/{subaccountId} Returns combined cost basis, proceeds, and gains/losses for a subaccount and time range.

curl --request GET \
     --url 'https://api.anchorage.com/v2/tax/gains/summary/{subaccountId}?startDateTime=2023-01-01T00:00:00Z&endDateTime=2025-03-01T23:59:59Z' \
     --header 'Api-Access-Key: {API Key}' \
     --header 'accept: application/json'

{
  "data": {
    "longTerm": { "assetType": "USD", "quantity": "0" },
    "shortTerm": { "assetType": "USD", "quantity": "-87.133251361246620162189357418267650072" },
    "total": { "assetType": "USD", "quantity": "-87.133251361246620162189357418267650072" }
  }
}

GET /v2/tax/gains/costbasis/{subaccountId} Returns per-disposal gain/loss records broken down into short-term and long-term, with cost basis and proceeds.

curl --request GET \
     --url 'https://api.anchorage.com/v2/tax/gains/costbasis/{subaccountId}?startDateTime=2023-01-01T00:00:00Z&endDateTime=2025-03-01T23:59:59Z' \
     --header 'Api-Access-Key: {API Key}' \
     --header 'accept: application/json'

{
  "data": [
    {
      "acquisitionTxId": "995024a3-bcc1-5430-a2fd-7fc448cd2dd1",
      "cost": { "assetType": "USD", "quantity": "40.012" },
      "costBasisDate": "2024-12-04T20:25:59.509Z",
      "dispositionTxId": "61ab9b9f-f2e3-5342-aa8f-1d56386379d6",
      "gain": { "assetType": "USD", "quantity": "-0.0419952" },
      "gainType": "short-term",
      "proceeds": { "assetType": "USD", "quantity": "39.9700048" },
      "saleDate": "2024-12-04T20:38:37.544Z",
      "sold": { "assetType": "USDC", "quantity": "40" },
      "taxYear": "2024"
    }
  ]
}

Step 5: Fetch tax forms

GET /v2/tax/subaccounts/{subaccountId}/forms Returns pre-signed download links for a subaccount’s tax forms. Links are time-limited.

curl --request GET \
     --url https://api.anchorage-staging.com/v2/tax/subaccounts/{subaccountId}/forms \
     --header 'Api-Access-Key: {API Key}' \
     --header 'accept: application/json'

{
  "data": [
    {
      "forms": [
        {
          "downloadLink": "<pre-signed S3 URL — use immediately, expires in 1 hour>",
          "formType": "1099_B"
        }
      ],
      "subaccountId": "32ee4b77-7f2a-4486-86f8-01c6bc8e4fda"
    }
  ]
}

GET /v2/tax/clients/{customerId}/forms Returns forms for all subaccounts belonging to a customerId. Use customerId as affiliateId.

curl --request GET \
     --url https://api.anchorage-staging.com/v2/tax/clients/{customerId}/forms \
     --header 'Api-Access-Key: {API Key}' \
     --header 'accept: application/json'

{
  "data": [
    {
      "forms": [],
      "subaccountId": "bb41b0c4-b3d7-4132-94d0-9ae2293bca5e"
    },
    {
      "forms": [
        {
          "downloadLink": "<pre-signed S3 URL — use immediately, expires in 1 hour>",
          "formType": "1099_B"
        }
      ],
      "subaccountId": "32ee4b77-7f2a-4486-86f8-01c6bc8e4fda"
    }
  ]
}

Step 6: Tag or untag a transaction

IRA transactions need a tag identifying the retirement-specific event type before they can be reflected correctly on 1099-R and Form 5498 reporting. POST /v2/tax/transaction/{transactionId}/tag tag values:

Value	Description
`contribution`	Contribution to a retirement account.
`transfer-in`	Assets transferred into the account.
`conversion`	Conversion (e.g., Traditional IRA to Roth IRA).
`distribution`	Distribution from the account. Requires `distributionCode`.
`transfer-out`	Assets transferred out of the account.
`recharacterization`	Recharacterized contribution.
`late-rollover`	Late rollover. Requires `postponedLateReason`.
`postponed`	Postponed contribution. Requires `postponedLateReason`.
`rollover`	Rollover contribution.

distributionCode is required when tag is distribution, and must be a valid IRS Form 1099-R distribution code (for example, 7 for a normal distribution or 4 for death). postponedLateReason is required when tag is postponed or late-rollover.

curl --request POST \
     --url https://api.anchorage-staging.com/v2/tax/transaction/{transactionId}/tag \
     --header 'Api-Access-Key: {API Key}' \
     --header 'accept: application/json' \
     --header 'content-type: application/json' \
     --data '{
  "accountId": "cb80459c-a930-444e-8f17-69ba9d0e122f",
  "tag": "distribution",
  "distributionCode": "7",
  "taxYear": "2025"
}'

{
  "data": {
    "status": "accepted"
  }
}

To remove a tag, use DELETE /v2/tax/transaction/{transactionId}/tag:

curl --request DELETE \
     --url https://api.anchorage-staging.com/v2/tax/transaction/{transactionId}/tag \
     --header 'Api-Access-Key: {API Key}' \
     --header 'accept: application/json'

{
  "data": {
    "status": "accepted"
  }
}

​Tax data overview

​HIFO accounting method

​Tax reporting partnership

​Transaction types

​Cost basis tracking

​subaccountId and customerId mapping

​Tax terminology

​Critical considerations

​Supported tax forms

​Integration steps

​Step 1: Review tax transactions

​Step 2: Update missing cost basis

​Step 3: View asset inventory

​Step 4: Review cost basis and gains

​Step 5: Fetch tax forms

​Step 6: Tag or untag a transaction

Tax data overview

HIFO accounting method

Tax reporting partnership

Transaction types

Cost basis tracking

`subaccountId` and `customerId` mapping

Tax terminology

Critical considerations

Supported tax forms

Integration steps

Step 1: Review tax transactions

Step 2: Update missing cost basis

Step 3: View asset inventory

Step 4: Review cost basis and gains

Step 5: Fetch tax forms

Step 6: Tag or untag a transaction