Define thresholds at which an invoice will be sent, and the subscription advanced to a new billing period. Pass an empty string to remove previously-defined thresholds.

The coupons to redeem into discounts for the subscription item.

Specifies which fields in the response should be expanded.

Set of [key-value pairs](https://docs.stripe.com/api/metadata) that you can attach to an object. This can be useful for storing additional information about the object in a structured format. Individual keys can be unset by posting an empty value to them. All keys can be unset by posting an empty value to `metadata`.

Indicates if a customer is on or off-session while an invoice payment is attempted. Defaults to `false` (on-session).

Controls how Stripe handles payment when a subscription update requires payment and `collection_method=charge_automatically`.

The ID of the price object. One of `price` or `price_data` is required. When changing a subscription item's price, `quantity` is set to 1 unless a `quantity` parameter is provided.

Data used to generate a new [Price](https://docs.stripe.com/api/prices) object inline. One of `price` or `price_data` is required.

Determines how to handle [prorations](https://docs.stripe.com/billing/subscriptions/prorations) when the billing cycle changes (e.g., when switching plans, resetting `billing_cycle_anchor=now`, or starting a trial), or if an item's `quantity` changes. The default value is `create_prorations`.

If set, the proration will be calculated as though the subscription was updated at the given time. This can be used to apply the same proration that was previewed with the [upcoming invoice](/api/invoices/create_preview) endpoint.

The quantity you'd like to apply to the subscription item you're creating.

A list of [Tax Rate](https://docs.stripe.com/api/tax_rates) ids. These Tax Rates will override the [`default_tax_rates`](https://docs.stripe.com/api/subscriptions/create#create_subscription-default_tax_rates) on the Subscription. When updating, pass an empty string to remove previously-defined tax rates.