Create recurring app purchases
You can create and manage recurring app purchases, which are called "app subscriptions". This section teaches you how to create recurring charges based on time or usage, update the maximum amount that you can charge a merchant each time, and cancel recurring charges using the Billing API. This section is for Partners who charge merchants to use their apps.
Upgrading and downgrading apps
Anchor link to section titled "Upgrading and downgrading apps"Merchants are permitted to have only one subscription to your app at a time. This means that, if a merchant upgrades or downgrades your app, then the old subscription is canceled and replaced with a new subscription. When the merchant upgrades or downgrades the app, the new subscription takes the same 30-day app billing cycle as the previous purchase. This also applies when a merchant uninstalls or reinstalls an app.

If the new subscription includes trial days, then the merchant is still charged on the beginning of the next 30-day app billing cycle, but the bill includes a prorated credit to account for the trial days.

Upgrading an app
Anchor link to section titled "Upgrading an app"When a merchant upgrades to a more expensive subscription, Shopify prorates the amount of the charge with the same billing cycle. For example, if a merchant begins a 30-day billing cycle on a $5.00 plan, and then upgrades to a $15.00 plan on day 15 of the billing cycle, then the merchant is charged $5.00 + ($15.00 - $5.00) * (15/30) = $10.00 USD.
Downgrading an app
Anchor link to section titled "Downgrading an app"When a merchant downgrades, Shopify generates a prorated app credit for the merchant while retaining the same billing cycle. For example, if a merchant begins a 30-day billing cycle on a $20.00 plan, and then downgrades to a $10.00 plan on day 15 of the billing cycle, then the merchant is offered an application credit for ($20.00 - $10.00) * (15/30) = $5.00 USD. The Partner payout is automatically adjusted based on the issued credit and the Partner revenue share.