Stripe Extension - Subscription ID Field

The Stripe Extension includes a Subscription ID field which you'll find in the Workflow section of the Gravity Forms Form Editor.

For example, this would allow you to create a form specifically for subscription requests which can be approved by an authorized with a one-click approval link in an email and the refund will be processed automatically without having to log in to either WordPress or Stripe. Subscription ID

The purpose of this field is to facilitate the validation of a Subscription ID during form submission or a User Input step and provide some basic details about the subscription in the entry detail page, the workflow entry detail page, and the merge tag. 

By default, the field merge tag will output similar information to the entry detail page in the screenshot above. If you need to output just the Subscription ID without the payment details then you can use the "value" modifier. For example, {Subscription ID:1:value}

If you're not sure how your customers can access their Subscription ID then one way could be to use the {entry:transaction_id} merge tag in a notification which the customer receives immediately after their payment is processed.