When combining different Prices on a subscription, which parameter must remain the same?

When combining different Prices on a subscription in Stripe, the billing interval must remain the same. This is crucial because it ensures that the subscription's payment schedule is consistent across all items included in the subscription.

For example, if you have one Price set to bill monthly and another set to bill yearly, combining these two would lead to confusion in billing cycles and customer expectations. Uniform billing intervals help maintain a clear and manageable subscription flow, ensuring that all component Prices align logically in their charging frequency and allow for accurate calculations regarding billing and invoicing.

The other parameters, although important, do not need to be the same for combining Prices. Currency can differ as long as the system handles conversions correctly, customer type can vary according to different user profiles, and discount rates can apply individually to each Price within the subscription. Thus, maintaining the same billing interval is key to ensuring the coherence of the subscription model.