# Customer codes

Source: https://developer.avalara.com/ecommerce-integration-guide/designing/customer-codes/

**Element type:** Required

**Endpoints/models used:** [CreateTransactionModel](https://developer.avalara.com/api-reference/avatax/rest/v2/models/CreateTransactionModel/)

Your integration must pass your unique customer IDs in the `customerCode` field. This field is required because it can be used to identify exempt customers within AvaTax, whether through AvaTax or Exemption Certificate Management. This code represents the customer identifier from the source system being sent within the request.

[![Closed](https://avalara-devdocs-prod.mcoutput.com/avatax-for-ecom/Content/Skins/Default/Stylesheets/Images/transparent.gif)Example](javascript:void\(0\);)

```
{  ...  "type": "SalesInvoice",  "companyCode": "DEFAULT",  "date": "2024-07-10",  "code": "XYZ",  "customerCode": "ABC",  "purchaseOrderNo": "123456789",  "commit": true,  "currencyCode": "USD",  "description": "Yarn"} 
```