# Add tags to Managed Service for Apache Flink applications
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This section describes how to add key-value metadata tags to Managed Service for Apache Flink applications. These tags can be used for the following purposes:
+ Determining billing for individual Managed Service for Apache Flink applications. For more information, see [Using Cost Allocation Tags](https://docs.aws.amazon.com/awsaccountbilling/latest/aboutv2/cost-alloc-tags.html) in the *Billing and Cost Management Guide*.
+ Controlling access to application resources based on tags. For more information, see [Controlling Access Using Tags](https://docs.aws.amazon.com/IAM/latest/UserGuide/access_tags.html) in the *AWS Identity and Access Management User Guide*.
+ User-defined purposes. You can define application functionality based on the presence of user tags.

Note the following information about tagging:
+ The maximum number of application tags includes system tags. The maximum number of user-defined application tags is 50.
+ If an action includes a tag list that has duplicate `Key` values, the service throws an `InvalidArgumentException`.

**Topics**
+ [Add tags when an application is created](how-tagging-create.md)
+ [Add or update tags for an existing application](how-tagging-add.md)
+ [List tags for an application](how-tagging-list.md)
+ [Remove tags from an application](how-tagging-remove.md)