How can I reference a Stripe plan with a predefined trial period when creating a subscription?

When creating a subscription with a trial period, you have two options:

1. Set the trial on the subscription request:
   This is what you’re doing with the TrialEnd property in your code. When you provide TrialEnd, it overrides any trial period defined in the plan (or price) itself.

2. Define a trial on the plan (or price) in Stripe:
   You can configure the plan’s default trial period—by setting the trial_period_days parameter when creating the plan (or, in our newer API, when creating the price). Once your plan (or price) is configured with a trial period, you simply reference that plan’s identifier in your subscription items and omit the TrialEnd property in your SubscriptionCreateOptions. When you do this, Stripe uses the default trial period defined in the plan/price.

For example, if you create a plan (or price) via the API or Dashboard with a one‑month trial (i.e. trial_period_days set to 30), then your subscription creation code would look like this:

CSHARPCopied
// Create subscription without explicitly setting TrialEnd
SubscriptionCreateOptions options = new()
{
    Customer = customerId,
    Items = new List<SubscriptionItemOptions>()
};

// Add subscription items (each with a price that has a trial configured)
foreach (string price in Settings.ParsePriceIds())
    options.Items.Add(new SubscriptionItemOptions { Price = price });

// Create subscription
var service = new SubscriptionService();
await service.CreateAsync(options);

In this case, the trial period comes from the trial_period_days specified when you created the plan (or price). This approach means you only have to manage the trial period once—when setting up the plan—rather than overriding it every time you create a subscription.

Summary:

• Define a trial period on your plan/price during creation (using trial_period_days).
• Reference that plan/price in your subscription creation.
• Omit the TrialEnd property on the subscription request to allow the plan’s default trial to be applied.

This method makes your configuration easier to manage and keeps your subscription creation code simpler.