I have deactivated a few Square plans. And I am fetching the plans from the API. But these plans having the is_deleted value is false only.
How can I know whether a Plan is active or inactive from the API?
When a plan is deactivated it will continue till the end of the next billing cycle. At this time immediately canceling a subscription isn’t currently available. 
Actually my question is only related to the Square Plan and not Subscription.
I deactivated plans in Square. And I am getting those plans are still active in the response. Please reply to my question.
I am using the endpoint is Catalog object and the Type is SUBSCRIPTION_PLAN.
What’s the plan_id that your seeing this behavior with?
All of the deactivated plans are having this issue.
One of the plan id is “id”: “MANADDVZNKR5V73UMVCAENSZ”. For this plan, getting the is_deleted value is false, even though it is inactive.
Sorry, this is the expected behavior for a plan. It can be deactivated however the ability to delete a plan from the Catalog isn’t currently possible which is why is_deleted is set to false.