---
title: "Allow a blockchain address to transfer and burn fungible tokens"
method: POST
path: "/v3/blockchain/token/approve"
tags: ["Fungible Tokens (ERC-20 or compatible)"]
---

# Allow a blockchain address to transfer and burn fungible tokens

`POST /v3/blockchain/token/approve`

## Request

- Base URL: `https://api.tatum.io`
- URL: `https://api.tatum.io/v3/blockchain/token/approve`
- Auth: API key in header `x-api-key`

/v3/blockchain/token/approve

**2 credits per API call**

Allow a blockchain address (the `spender` parameter in the request body) to transfer and burn fungible tokens on behalf of the smart contract owner.

This API is supported for the following blockchains:

*   BNB Smart Chain
*   Celo
*   Ethereum
*   Harmony
*   Klaytn
*   Polygon
*   Flare
*   Cronos
*   Base
*   Avalanche
*   Fantom
*   Optimism

**Signing a transaction**  
When allowing a blockchain address to transfer and burn fungible tokens, you are charged a fee for the transaction, and you must sign the transaction with the private key of the blockchain address from which the fee will be deducted.

Providing the private key in the API is not a secure way of signing transactions, because the private key can be stolen or exposed. Your private keys should never leave your security perimeter. You should use the private keys only for testing a solution you are building on the **testnet** of a blockchain.

For signing transactions on the **mainnet**, we strongly recommend that you use the Tatum [Key Management System (KMS)](https://github.com/tatumio/tatum-kms) and provide the signature ID instead of the private key in the API. Alternatively, you can use the [Tatum JavaScript client](https://github.com/tatumio/tatum-js/tree/v2).

## Query parameters

- `testnetType` 'ethereum-sepolia' | 'flare-coston' | 'flare-coston2' | 'flare-songbird': Specifies the testnet type. The default is ethereum-sepolia for Ethereum (ETH) currency and flare-coston for Flare (FLR) currency. Valid testnet types depend on the specified currency.

## Headers

- `x-testnet-type` Schema (unresolved $ref)

## Request body

- union
  - ApproveErc20
    - `chain` 'ETH' | 'BSC' | 'MATIC' | 'KLAY' | 'ONE' | 'FLR' | 'CRO' | 'BASE' | 'AVAX' | 'OPTIMISM' | 'FTM', required: The blockchain to work with
    - `contractAddress` string, required: The address of the smart contract
    - `spender` string, required: The blockchain address to be allowed to transfer or burn the fungible tokens
    - `amount` string, required: The amount of the tokens allowed to be transferred or burnt
    - `fromPrivateKey` string, required: The private key of the smart contract's owner; the fee will be deducted from the owner's address
    - `fee` CustomFee: The custom defined fee; if not present, will be calculated automatically
      - `gasPrice` string, required: The price for one gas unit (in Gwei)
      - `gasLimit` string, required: The maximum number of gas units that you are willing to spend on processing the transaction at the provided gas price
    - `nonce` number: The nonce to be set to the transaction; if not present, the last known nonce will be used
  - ApproveErc20KMS
    - `chain` 'ETH' | 'BSC' | 'MATIC' | 'KLAY' | 'ONE', required: The blockchain to work with
    - `contractAddress` string, required: The address of the smart contract
    - `spender` string, required: The blockchain address to be allowed to transfer or burn the fungible tokens
    - `amount` string, required: The amount of the tokens allowed to be transferred or burnt
    - `signatureId` string, uuid, required: The KMS identifier of the private key of the smart contract's owner; the fee will be deducted from the owner's address
    - `fee` CustomFee: The custom defined fee; if not present, will be calculated automatically
      - `gasPrice` string, required: The price for one gas unit (in Gwei)
      - `gasLimit` string, required: The maximum number of gas units that you are willing to spend on processing the transaction at the provided gas price
    - `nonce` number: The nonce to be set to the transaction; if not present, the last known nonce will be used
  - ApproveCeloErc20
    - `chain` 'CELO', required: The blockchain to work with
    - `contractAddress` string, required: The address of the smart contract
    - `spender` string, required: The blockchain address to be allowed to transfer or burn the fungible tokens
    - `amount` string, required: The amount of the tokens allowed to be transferred or burnt
    - `fromPrivateKey` string, required: The private key of the smart contract's owner; the fee will be deducted from the owner's address
    - `feeCurrency` 'CELO' | 'CUSD' | 'CEUR', required: The currency in which the transaction fee will be paid
    - `fee` CustomFee: The custom defined fee; if not present, will be calculated automatically
      - `gasPrice` string, required: The price for one gas unit (in Gwei)
      - `gasLimit` string, required: The maximum number of gas units that you are willing to spend on processing the transaction at the provided gas price
    - `nonce` number: The nonce to be set to the transaction; if not present, the last known nonce will be used
  - ApproveCeloErc20KMS
    - `chain` 'CELO', required: The blockchain to work with
    - `contractAddress` string, required: The address of the smart contract
    - `spender` string, required: The blockchain address to be allowed to transfer or burn the fungible tokens
    - `amount` string, required: The amount of the tokens allowed to be transferred or burnt
    - `signatureId` string, uuid, required: The KMS identifier of the private key of the smart contract's owner; the fee will be deducted from the owner's address
    - `feeCurrency` 'CELO' | 'CUSD' | 'CEUR', required: The currency in which the transaction fee will be paid
    - `fee` CustomFee: The custom defined fee; if not present, will be calculated automatically
      - `gasPrice` string, required: The price for one gas unit (in Gwei)
      - `gasLimit` string, required: The maximum number of gas units that you are willing to spend on processing the transaction at the provided gas price
    - `nonce` number: The nonce to be set to the transaction; if not present, the last known nonce will be used

## Response `200`

OK

- union
  - TransactionHash
    - `txId` string, required: The hash (ID) of the transaction
  - SignatureId
    - `signatureId` string, uuid, required: The internal Tatum ID of the prepared transaction for Key Management Sysytem (KMS) to sign<br/>This is different from the <code>signatureId</code> parameter that you provided in the request body. The <code>signatureId</code> parameter in the request body specifies the signature ID associated with the private key in KMS.

## Other responses

- `400`: Bad Request
- `401`: Unauthorized. Not valid or inactive subscription key present in the HTTP Header.
- `403`: Forbidden. The request is authenticated, but it is not possible to perform the operation due to logical error or invalid permissions.
- `500`: Internal server error. There was an error on the server during the processing of the request.

---

[API](https://skmtc.dev/tatum/apis/smart-contracts.md) - [All operations](https://skmtc.dev/tatum/apis/smart-contracts/llms.txt) - [OpenAPI document](https://skmtc.dev/tatum/apis/smart-contracts/revisions/c0146043bb37?raw)