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# Handling Exemptions

Sales tax exemptions apply when customers such as non-profits, resellers, and government agencies provide a valid exemption certificate. To ensure compliance, you must attach that certificate (or mark the order as exempt) when creating your cart; once an order is finalized, you cannot retroactively add exemptions.

This guide walks you through:

* What you need before attaching an exemption certificate
* Two ways to apply an exemption: directly by certificate ID or automatically through matching.
* Best practices and common errors to avoid.

By following these steps, you can ensure exempt transactions are processed smoothly and remain compliant with state requirements.

## What You'll Need

* A certificate already created in TaxCloud and showing an “Active” status. (Use the [Create Exemption Certificate](https://docs.taxcloud.com/api-reference/api-reference/sales-tax-api/exemption-certificate/create-exemption-certificate) endpoint if you don't have the certificate yet).  
* Either the certificate’s ID or enough matching data: `customerID`, destination.state, and your `connectionID`, for auto-match to work.

## Applying Exemption Certificates

Once you have an active certificate, you can apply it to a cart in one of three ways:

### Option A – Direct attach by ID

Add an exemption object with `exemptionID` to the same cart payload you used earlier.

#### Sample Request (Python)

```py
payload = {
    "items": [
        {
            "currency": { "currencyCode": "USD" },
            "customerId": "customer-453",
            "destination": { "city": "Austin", "state": "TX", "zip": "78701" },
            "origin": { "city": "Austin", "state": "TX", "zip": "78701" },
            "exemption": { "exemptionId": "a1b2c3d4-ID" },
            "lineItems": [
                {
                    "index": 0,
                    "itemId": "item-1",
                    "price": 100,
                    "quantity": 1,
                    "tic": 0
                }
            ]
        }
    ]
}
```

TaxCloud validates the certificate ID, confirms it is active for that destination state, and returns zero tax on the response.

### Option B – Auto-match

If you don’t know the certificate ID, set “exemption”: `“isExempt”: true` in your cart. TaxCloud will try to find an active certificate that matches the same `connectionID`, `customerID`, and destination state. If a match is found, tax is zeroed. If no certificate exists, the cart (and later the order) is flagged **Exempt—No certificate** and will need manual resolution before filing.

## Best Practices

* Store certificate IDs in your customer profile so you can attach them explicitly and avoid auto-match surprises.  
* Certificates can expire; monitor expiry dates and renew as needed.
* A single buyer might hold multiple, state-specific certificates—always match the destination state.  
* If you mistakenly mark `isExempt: true` and no valid certificate exists, TaxCloud flags the order as **Exempt—No certificate**, which must be resolved before the transaction can be filed.

## Common Errors

* 400 CertificateNotValid – Invalid Certificate ID.  
* 422 IncorrectCertificate– Missing certificate details.

## Next Step

With tax (or zero tax) confirmed, proceed to [Convert Carts to Orders](https://docs.taxcloud.com/guides/workflows/real-time-api/convert-carts-to-orders) to convert the transaction, and if complete, record the liability. For comprehensive knowledge on managing your tax exemptions, please see our [guide here](https://docs.taxcloud.com/guides/core-concepts/managing-tax-exemptions).