# IAM JSON policy elements: Id
Id

The `Id` element specifies an optional identifier for the policy. The ID is used differently in different services. ID is allowed in resource-based policies, but not in identity-based policies.

For services that let you set an `ID` element, we recommend you use a UUID (GUID) for the value, or incorporate a UUID as part of the ID to ensure uniqueness. 

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#### [ JSON ]

****  

```
{
  "Version":"2012-10-17",		 	 	 
  "Id": "cd3ad3d9-2776-4ef1-a904-4c229d1642ee",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": "s3:ListAllMyBuckets",
      "Resource": "*"
    }
  ]
}
```

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**Note**  
Some AWS services (for example, Amazon SQS or Amazon SNS) might require this element and have uniqueness requirements for it. For service-specific information about writing policies, refer to the documentation for the service you're working with.