# Build Approval Transaction

If your allowance is not sufficient, this endpoint can help you initiate an ERC20 approval transaction.

{% openapi src="<https://3694085950-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-Mcs9EhDrgbKHodtcAT6%2Fuploads%2F992nLSFootyLzNGT3OSd%2Fopenapi.json?alt=media&token=dbdd978e-3fd3-4af0-a7aa-36ce013023ad>" path="/approveTx" method="get" %}
[openapi.json](https://3694085950-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-Mcs9EhDrgbKHodtcAT6%2Fuploads%2F992nLSFootyLzNGT3OSd%2Fopenapi.json?alt=media\&token=dbdd978e-3fd3-4af0-a7aa-36ce013023ad)
{% endopenapi %}

{% hint style="info" %}
**NOTE :** The spender should be the `contractAddress` in the response of [Get Quote](https://docs.xy.finance/bridge-aggregator-integration/xy-finance-api-multiple-bridges-aggregator/get-quote).\
e.g. `routes[{ROUTE_INDEX}]["contractAddress"]`
{% endhint %}

{% hint style="info" %}
Here you can find our full [API reference](https://aggregator-api.xy.finance/v1/docs)
{% endhint %}