---
title: "Bid for an asset at the NFT auction"
method: POST
path: "/v3/blockchain/auction/bid"
tags: ["Auction"]
---

# Bid for an asset at the NFT auction

`POST /v3/blockchain/auction/bid`

## Request

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

/v3/blockchain/auction/bid

**2 credits per API call**

Bid for an asset listed on the NFT auction.

You can buy the asset either for the native blockchain assets (for example, ETH, BSC, and so on) or for the fungible tokens of the blockchain.

*   If you want to pay for the asset with the **native assets**, send the required amount of the assets with the API call.
*   If you want to pay with the **fungible tokens**, [allow the auction smart contract to access your tokens](https://apidoc.tatum.io/tag/Fungible-Tokens-\(ERC-20-or-compatible\)#operation/Erc20Approve) before bidding for the asset. When you make the API call, the auction smart contract will deduct the required amount of the tokens from the smart contract where you hold the tokens.

After you have purchased the asset, it is in a pending state until [the auction is settled](#operation/SettleAuction). Settling the auction means that the asset is transferred to the buyer, the amount is transferred to the seller, and the fee is transferred to the fee recipient of the auction.

For the complete information about how the bidding/purchase process at an auction works, see the API for [creating an NFT auction](#operation/GenerateAuction).

This API is supported for the following blockchains:

*   BNB Smart Chain
*   Celo
*   Ethereum
*   Harmony
*   Klaytn
*   Polygon

**The "execution reverted" message**  
When making this API call, you may get the following message:  
`Although one or more Error Occurred [execution reverted] Contract Execution Completed`  
This message is a result of the auction version check and has no impact on completing the API call. You can safely ignore it.

**Signing a transaction**  
When bidding for an asset at the NFT auction, 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).

## Request body

- union
  - BidOnAuction
    - `chain` 'ETH' | 'ONE' | 'BSC' | 'KLAY' | 'MATIC', required: Blockchain to work with.
    - `contractAddress` string, required: Address of the auction smart contract.
    - `erc20Address` string: Optional address of the ERC20 token, which will be used as a selling currency of the NFT.
    - `bidder` string: In case of the ERC20 auction, it's possible to bid on behalf of someone else. This value is the address of the bidder, which should approve spending of the ERC20 tokens for the Auction contract. This could be used for a bidding from the custodial wallet address.
    - `id` string, required: ID of the auction.
    - `bidValue` string, required: Amount of the assets to be bid. This must include auction fee.
    - `fromPrivateKey` string, required: Private key of sender address. Private key, or signature Id must be present.
    - `nonce` number: The nonce to be set to the transaction; if not present, the last known nonce will be used
    - `fee` object: Custom defined fee. If not present, it will be calculated automatically.
      - `gasLimit` string, required: Gas limit for transaction in gas price.
      - `gasPrice` string, required: Gas price in Gwei.
  - BidOnAuctionKMS
    - `chain` 'ETH' | 'ONE' | 'BSC' | 'KLAY' | 'MATIC', required: Blockchain to work with.
    - `contractAddress` string: Address of the auction smart contract.
    - `erc20Address` string: Optional address of the ERC20 token, which will be used as a selling currency of the NFT.
    - `bidder` string: In case of the ERC20 auction, it's possible to bid on behalf of someone else. This value is the address of the bidder, which should approve spending of the ERC20 tokens for the Auction contract. This could be used for a bidding from the custodial wallet address.
    - `id` string, required: ID of the auction.
    - `bidValue` string, required: Amount of the assets to be bid. This must include auction fee.
    - `signatureId` string, uuid, required: Identifier of the private key associated in signing application. Private key, or signature Id must be present.
    - `index` number: If signatureId is mnemonic-based, this is the index to the specific address from that mnemonic.
    - `nonce` number: The nonce to be set to the transaction; if not present, the last known nonce will be used
    - `fee` object: Custom defined fee. If not present, it will be calculated automatically.
      - `gasLimit` string, required: Gas limit for transaction in gas price.
      - `gasPrice` string, required: Gas price in Gwei.
  - BidOnAuctionCelo
    - `chain` 'CELO', required: Blockchain to work with.
    - `feeCurrency` 'CELO' | 'CUSD' | 'CEUR', required: The currency in which the transaction fee will be paid
    - `contractAddress` string, required: Address of the auction smart contract.
    - `erc20Address` string: Optional address of the ERC20 token, which will be used as a selling currency of the NFT.
    - `bidder` string: In case of the ERC20 auction, it's possible to bid on behalf of someone else. This value is the address of the bidder, which should approve spending of the ERC20 tokens for the Auction contract. This could be used for a bidding from the custodial wallet address.
    - `id` string, required: ID of the auction.
    - `bidValue` string, required: Amount of the assets to be bid. This must include auction fee.
    - `fromPrivateKey` string, required: Private key of sender address. Private key, or signature Id must be present.
    - `nonce` number: The nonce to be set to the transaction; if not present, the last known nonce will be used
    - `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
  - BidOnAuctionCeloKMS
    - `chain` 'CELO', required: Blockchain to work with.
    - `feeCurrency` 'CELO' | 'CUSD' | 'CEUR', required: The currency in which the transaction fee will be paid
    - `contractAddress` string, required: Address of the auction smart contract.
    - `erc20Address` string: Optional address of the ERC20 token, which will be used as a selling currency of the NFT.
    - `bidder` string: In case of the ERC20 auction, it's possible to bid on behalf of someone else. This value is the address of the bidder, which should approve spending of the ERC20 tokens for the Auction contract. This could be used for a bidding from the custodial wallet address.
    - `id` string, required: ID of the auction.
    - `bidValue` string, required: Amount of the assets to be bid. This must include auction fee.
    - `signatureId` string, uuid, required: Identifier of the private key associated in signing application. Private key, or signature Id must be present.
    - `index` number: If signatureId is mnemonic-based, this is the index to the specific address from that mnemonic.
    - `nonce` number: The nonce to be set to the transaction; if not present, the last known nonce will be used
    - `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

## 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)