Max--

[wise lark]

You configure how you want to set up prorations on your end. Here's a guide about those: https://stripe.com/docs/billing/subscriptions/prorations

[uneven flicker]

Thanks for getting back to me. What will happen if the user has a subscription, and I am sending through Zapier the subscription again with a coupon for 3 times 1 month free?

What is the default value?

as it says here "When prorations are disabled, customers are billed the full amount at the new price when the next invoice is generated."

Does this mean that the subscription will overlap and won't prorate?

[wise lark]

You choose if you want prorations to occur or not. Also, we have no context on Zapier as we don't support 3rd party connectors in this server. Our support folks might be able to help you out better: https://support.stripe.com/contact

[uneven flicker]

I just tried using the test clock. When I send a new subscription they just both appeared in the customer. How can I do so when a new subscription is created in the contact and it already exist to merge and prorate?

[wise lark]

How can I do so when a new subscription is created in the contact and it already exist to merge and prorate?
You can't merge subscriptions. Customers can have multiple active subscriptions. If you want to add additional items to the Subscription, you can do that by updated the Subscription with a new item : https://stripe.com/docs/api/subscriptions/update#update_subscription-items-price