Send Crypto Transactions with the Finrock API

Finrock gives you a single POST /dac/v1/transaction endpoint to move funds across all supported blockchains — whether you are sending to an external wallet, shifting balances between sub-accounts, or pushing assets to a connected exchange. This guide covers every parameter you need, explains destination and source types, shows you how to estimate fees before committing, and explains how to use idempotency keys so retried requests never result in a double-spend.

Overview

Submitting a transaction requires four core fields: the asset ticker, the amount, a source_type, and a destination_type. Additional fields control fee behaviour, AML tracking, bulk payouts, and idempotency. Endpoint: POST https://api.finrock.io/dac/v1/transaction

Destination Types

The destination_type field tells Finrock where the funds are going. Choose the value that matches your recipient:

EXTERNAL

Send to any address outside your Finrock workspace — for example, a customer’s self-custody wallet or a third-party exchange deposit address.

INTERNAL

Move funds into your own sub-account within the workspace — for example, pulling balance from a connected exchange into your custody wallet.

SUBACCOUNT

Transfer to a different sub-account within the same workspace — for example, moving funds from a trading desk sub-account to a treasury sub-account.

EXCHANGE

Send funds to a connected exchange — for example, depositing collateral to Binance or Kraken from your Finrock wallet.

Source Types

The source_type field tells Finrock where the funds originate:

Value	Description
`INTERNAL`	Funds originate from your Finrock workspace wallet
`EXCHANGE`	Funds originate from a connected exchange outside your workspace

Use source_id to specify a particular address or address label within your workspace when you want to spend from a specific balance rather than the aggregate wallet balance. For XRP and XLM, use source_tag to identify the originating address tag.

Creating a Transaction

The example below sends 100 USDT on the Tron network to an external wallet address:

curl --request POST \
     --url https://api.finrock.io/dac/v1/transaction \
     --header 'Authorization: Token {JWT}' \
     --header 'x-api-key: YOUR_API_KEY' \
     --header 'content-type: application/json' \
     --header 'accept: application/json' \
     --data '{
       "asset": "USDT_TRX",
       "amount": 100.00,
       "source_type": "INTERNAL",
       "destination_type": "EXTERNAL",
       "destination_id": "TXyzAbcDefGhiJklMnoPqrStuVwx",
       "memo": "Payment for invoice #1234",
       "sequence_id": "order-8472"
     }'

const response = await fetch('https://api.finrock.io/dac/v1/transaction', {
  method: 'POST',
  headers: {
    'Authorization': 'Token YOUR_JWT',
    'x-api-key': 'YOUR_API_KEY',
    'Content-Type': 'application/json',
    'Accept': 'application/json',
  },
  body: JSON.stringify({
    asset: 'USDT_TRX',
    amount: 100.00,
    source_type: 'INTERNAL',
    destination_type: 'EXTERNAL',
    destination_id: 'TXyzAbcDefGhiJklMnoPqrStuVwx',
    memo: 'Payment for invoice #1234',
    sequence_id: 'order-8472',
  }),
});

const transaction = await response.json();
console.log(transaction);

All Request Parameters

Parameter	Type	Required	Description
`asset`	string	Yes	Asset ticker from the supported-assets list
`amount`	double	Yes	Transfer amount (max 8 decimal places)
`source_type`	string	Yes	`INTERNAL` or `EXCHANGE`
`source_id`	string	No	Specific address or label to spend from
`source_tag`	string	No	Address tag for XRP/XLM source addresses
`destination_type`	string	Yes	`EXTERNAL`, `INTERNAL`, `SUBACCOUNT`, or `EXCHANGE`
`destination_id`	string	Yes*	Target address, sub-account ID, or exchange ID (*required unless using `destinations`)
`destination_tag`	string	No	Destination tag for XRP/XLM recipients
`destinations`	array	No	Array of recipient objects for bulk UTXO payouts
`memo`	string	No	Note added to the transaction history
`sequence_id`	string	No	Unique string for idempotency (prevents double-spend on retry)
`max_amount`	boolean	No	When `true`, sends the maximum possible balance after fees are deducted
`aml_cid`	string	No	Your external customer ID, used to link this transaction to an AML subject

Sending the Maximum Balance

Set max_amount: true to instruct Finrock to calculate the maximum sendable amount after network fees and deduct accordingly. Omit amount when using this flag:

curl --request POST \
     --url https://api.finrock.io/dac/v1/transaction \
     --header 'Authorization: Token {JWT}' \
     --header 'x-api-key: YOUR_API_KEY' \
     --header 'content-type: application/json' \
     --header 'accept: application/json' \
     --data '{
       "asset": "BTC",
       "max_amount": true,
       "source_type": "INTERNAL",
       "destination_type": "EXTERNAL",
       "destination_id": "bc1qRecipientAddressHere"
     }'

Bulk UTXO Payouts

For UTXO-based chains (Bitcoin, Litecoin, Dogecoin, Dash, Bitcoin Cash), you can send to multiple recipients in a single transaction using the destinations array instead of a single destination_id. This significantly reduces total network fees compared to sending individual transactions.

curl --request POST \
     --url https://api.finrock.io/dac/v1/transaction \
     --header 'Authorization: Token {JWT}' \
     --header 'x-api-key: YOUR_API_KEY' \
     --header 'content-type: application/json' \
     --header 'accept: application/json' \
     --data '{
       "asset": "BTC",
       "source_type": "INTERNAL",
       "destination_type": "EXTERNAL",
       "destinations": [
         { "address": "bc1qAddress1Here", "amount": 0.05 },
         { "address": "bc1qAddress2Here", "amount": 0.12 },
         { "address": "bc1qAddress3Here", "amount": 0.03 }
       ],
       "sequence_id": "batch-payout-2024-001"
     }'

The destinations array is supported only on UTXO chains (BTC, LTC, DOGE, DASH, BCH). For EVM, Tron, Solana, and other account-based chains, use a single destination_id.

AML Tracking with `aml_cid`

If you have AML screening enabled, pass your internal customer identifier in the aml_cid field. Finrock forwards this value to the AML provider (Chainalysis) so every transaction is linked to the correct subject in your compliance records:

{
  "asset": "ETH",
  "amount": 1.5,
  "source_type": "INTERNAL",
  "destination_type": "EXTERNAL",
  "destination_id": "0xRecipientAddress",
  "aml_cid": "customer-uuid-abc123"
}

Fee Estimation

Before submitting a high-value transaction, call POST /dac/v1/estimate-fee to preview the expected network fee without committing the transaction:

curl --request POST \
     --url https://api.finrock.io/dac/v1/estimate-fee \
     --header 'Authorization: Token {JWT}' \
     --header 'x-api-key: YOUR_API_KEY' \
     --header 'content-type: application/json' \
     --header 'accept: application/json' \
     --data '{
       "asset": "BTC",
       "amount": 0.5,
       "fee_rate": 20
     }'

The fee_rate unit depends on the blockchain. Use this reference table:

Blockchain	Example Assets	Fee Rate Unit
UTXO	BTC, LTC, DASH, DOGE, BCH	Sat/Byte
EVM	ETH, BSC, POL, BASE	GWei
Tron	TRX, USDT_TRX	Sun
Ripple	XRP	Drop
Stellar	XLM	Stroop
Cardano	ADA	Lovelace
Solana	SOL	Lamport

For UTXO chains, amount is required in the fee estimation request because transaction size — and therefore fee — depends on the number of inputs needed to cover the output value.

Idempotency with `sequence_id`

Network timeouts and application retries can cause your code to call the transaction endpoint more than once for the same intended transfer. Pass a unique sequence_id string with every transaction request. If Finrock receives a second request with the same sequence_id for the same sub-account, it returns the result of the original transaction instead of creating a new one.

{
  "asset": "USDT_TRX",
  "amount": 500,
  "source_type": "INTERNAL",
  "destination_type": "EXTERNAL",
  "destination_id": "TRecipientAddressHere",
  "sequence_id": "withdrawal-user-42-2024-11-26-001"
}

Always use a sequence_id for withdrawal flows in production. Without it, a retry caused by a network error will create a duplicate transaction and move funds twice.

Transaction Statuses

After submission, poll the transactions endpoint or listen to webhooks for status updates. See Transaction Statuses in the Platform Reference for the full list of status values and their meanings. For a deep dive on preventing duplicate transactions, see Idempotency.

Get Started

Core Concepts

Guides

Platform Reference

Send Crypto Transactions with the Finrock API

Overview

Destination Types

EXTERNAL

INTERNAL

SUBACCOUNT

EXCHANGE

Source Types

Creating a Transaction

All Request Parameters

Sending the Maximum Balance

Bulk UTXO Payouts

AML Tracking with `aml_cid`

Fee Estimation

Idempotency with `sequence_id`

Transaction Statuses

​Overview

​Destination Types

EXTERNAL

INTERNAL

SUBACCOUNT

EXCHANGE

​Source Types

​Creating a Transaction

​All Request Parameters

​Sending the Maximum Balance

​Bulk UTXO Payouts

​AML Tracking with aml_cid

​Fee Estimation

​Idempotency with sequence_id

​Transaction Statuses

Overview

Destination Types

Source Types

Creating a Transaction

All Request Parameters

Sending the Maximum Balance

Bulk UTXO Payouts

AML Tracking with `aml_cid`

Fee Estimation

Idempotency with `sequence_id`

Transaction Statuses