# Single-use exemptions

Source: https://developer.avalara.com/ecommerce-integration-guide/transactions/exemptions/single-use-exemptions/

Use purchase order numbers in conjunction with customer codes to trigger a single use exemption. In this case, also store the purchase order number from the transaction in the customer's exemption record.

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

```
{  "lines": [      {    "number": "1",    "quantity": 1,    "amount": 100,    "taxCode": "PC002386",    "itemCode": "CARPET",    "description": "Carpeting"      }  ],        "addresses": {    "singleLocation": {    "line1": "2000 Main Street",    "city": "Irvine",    "region": "CA",    "country": "US",    "postalCode": "92614"      }  },  "type": "SalesInvoice",  "code": "InvoiceNumberHere",  "companyCode": "DEFAULT",  "date": "2024-07-17",  "customerCode": "ABC",  "purchaseOrderNo": "123456789",  "commit": true,  "currencyCode": "USD",  "description": "Carpeting and tools"} 
```