# Build a transaction: /transactions
## Build Transaction
`POST` `https://api.paraswap.io/transactions/:network`
Build parameters for a transaction with the response from `/prices` endpoint.
#### Path Parameters
Path parameters define the network on which the transaction will be executed. Since blockchain networks operate independently, specifying the correct network ensures that the API queries the right environment for liquidity and transaction execution.
| Name | Type | Description |
| ------- | ------ | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| network | number | Network ID. (Mainnet - 1, Optimism - 10, BSC - 56, Polygon - 137, Base - 8453, Arbitrum - 42161, Avalanche - 43114, Gnosis - 100, Sonic - 146, Unichain - 130, Plasma - 9745). |
#### Query Parameters
As an integrator, you can modify the behavior of the API call based on the Query parameters. This allows you to customize the response based on your needs.
| Name | Type | Description |
| ----------------- | ------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| gasPrice | string | Gas-price to be used for the transaction ***in wei***. |
| ignoreChecks | boolean | Allows the API to skip performing on-chain checks such as balances, allowances, as well as possible transaction failures.
\*Note: The response does not contain gas parameter when ignoreChecks is set to true.
Default: false
|
| ignoreGasEstimate | boolean | Allows the API to skip gas checks
\*Note: The response does not contain gas parameter when ignoreGasEstimate is set to true.
Default: false
|
| onlyParams | boolean | Allows the API to return the contract parameters only.
Default: false
|
| eip1559 | boolean | Allows the API to return EIP-1559 styled transaction with maxFeePerGas and maxPriorityFeePerGas paramters.
\*Note: We currently support EIP1559 transactions in the following chains:
Mainnet, Ropsten, and Avalanche.
Default: false
|
#### Request Body
The request body provides the details needed to execute a swap, including token details, amounts, pricing data, and user-specific parameters.
| Name | Type | Description |
| ------------------- | ------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| srcToken | string | Destination Token Address. *Only Token Symbol could be specified for tokens from* `/tokens`. |
| srcDecimals | integer | Source Token Decimals. (Can be omitted if Token Symbol is provided for `srcToken`). |
| destToken | string | Destination Token Address. *Only Token Symbol could be specified for tokens from* `/tokens`. |
| destDecimals | integer | Destination Token Decimals. (Can be omitted if Token Symbol is provided for `destToken`). |
| srcAmount | integer | Source Amount with decimals. Required if **side=SELL**. Could only be omitted if **slippage** is provided when **side=BUY** |
| destAmount | integer | Destination amount with decimals. Required if **side=BUY**. Could only be omitted if **slippage** is provided when **side=SELL**. |
| priceRoute | object | `priceRoute` from response body returned from `/prices` endpoint. `priceRoute` should be sent exactly as it was returned by the `/prices` endpoint. |
| slippage | integer | Allowed slippage percentage represented in basis points.
Eg: for 2.5% slippage, set the value to 2.5 \* 100 = 250; for 10% = 1000. Slippage could be passed instead of destAmount when side=SELL or srcAmount when side=BUY.
Min: 0; Max: 10000
|
| userAddress | string | Address of the caller of the transaction (`msg.sender`) |
| txOrigin | string | Whenever `msg.sender` (userAddress) i.e. address calling the Velora contract is different than the address sending the transaction, `txOrigin` must be passed along with `userAddress`. |
| receiver | string | Address of the Receiver (that will receive the output of the swap). Used for Swap\&Transfer. |
| partnerAddress | string | Address that will be entitled to claim fees or surplus.
\*Note: Fees have to be claimed from the Fee Claimer contract unless isSurplusToUser or isDirectFeeTransfer are used
|
| partnerFeeBps | string | If provided it is used together with partnerAddress. Should be in basis points percentage. Look at slippage parameter description for understanding better.
Eg: 200 (for 2% fee percent)
\*Note: Fees have to be claimed from the Fee Claimer contract unless isSurplusToUser or isDirectFeeTransfer are used
|
| partner | string | Your project name.
Used for providing analytics on your project swaps.
|
| permit | string | Hex string for the signature used for Permit. This can be used to avoid giving approval. *Helps in saving gas.* |
| deadline | integer | Timestamp (10 digit/seconds precision) till when the given transaction is valid. For a deadline of 5 minute, deadline: Math.floor(Date.now()/1000) + 300
E.g.: 1629214486
|
| isCapSurplus | boolean | Allows for capping the surplus at 1% maximum.
Default: true
|
| takeSurplus | boolean | Allows to collect surplus. Works with partnerAddress
Default: false
|
| isSurplusToUser | boolean | Specify if user should receive surplus instead of partner.
Default: false
|
| isDirectFeeTransfer | boolean | Specify if fees should be sent directly to the partner instead of registering them on FeeClaimer.
Default: false
|
**Example:**
Here’s an example of a successful and failed transaction.
{% tabs %}
{% tab title="200 Transaction Request Response (When onlyParams=false)" %}
```
{
"from": "0xa0b86991c6218b36c1d19d4a2e9eb0ce3606eb48",
"to": "0x6a000f20005980200259b80c5102003040001068",
"value": "0",
"data": "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",
"gasPrice": "16000000000",
"chainId": 1
}
```
{% endtab %}
{% tab title="400 Transaction Building Error" %}
```
{
"error": "Unable to process the transaction"
}
```
{% endtab %}
{% endtabs %}
#### Most common error messages
The following is a list of the most common error messages of the `/transactions` endpoint. Most are self-explanatory and can be self-solved, but feel free to contact Velora Support using the chat in the bottom right corner of this page.
* `Validation failed: permit signature should be lower than 706`
* `Validation failed: ` - params validation failed (message has the exact reason of failure)
* `Missing price route` - price route param is not passed
* `Missing srcAmount` (sell)
* `Cannot specify both slippage and destAmount` (sell)
* `Missing slippage or destAmount` (sell)
* `Missing slippage or srcAmount` (buy)
* `Source Amount Mismatch` (sell)
* `Destination Amount Mismatch` (buy)
* `Missing destAmount` (buy)
* `Cannot specify both slippage and srcAmount` (buy)
* `Network Mismatch`
* `Source Token Mismatch`
* `Destination Token Mismatch`
* `Contract method doesn't support swap and transfer`
* `Side Mismatch`
* `Source Decimals Mismatch`
* `Destination Decimals Mismatch`
* `It is not allowed to pass both params: "positiveSlippageToUser" and "takeSurplus".` - We advise removing "positiveSlippageToUser" because it is deprecated
* `When "isSurplusToUser"="true", "takeSurplus" must be also "true" and either "partnerAddress" or "partner" must be set`
* `When "isDirectFeeTransfer"="true", please also set "takeSurplus"="true" and provide partner/fee information via "partnerFeeBps" & "partnerAddress" or valid "partner" params; or add "referrer" param`
* `Internal Error while building transaction` - something went wrong during the transaction build
* `Unable to build transaction ` - something went wrong during the transaction build
* `It is not allowed to have limit-orders Dex or paraswappool Dex in route and 'ignoreChecks=true' together. Consider requesting the price with excluded limit-orders if you want to use 'ignoreChecks': &excludeDEXS=ParaSwapPool,ParaSwapLimitOrders`
* `It seems like the rate has changed, please re-query the latest Price`
* `The rate has changed, please re-query the latest Price`
* `This transaction has some errors and may fail. Please contact support for more details`
* `Not enough balance`
* `Not enough allowance given to TokenTransferProxy()`
* `Unable to check price impact` - src or dest tokens don’t have valid usd price