# `extendSubscriptionItemFreeTrial()`

Extends the free trial for the given Subscription Item.

Returns the updated [`BillingSubscriptionItem`](/content/docs/reference/backend/types/billing-subscription-item/index.html) object.

```javascript
function extendSubscriptionItemFreeTrial(subscriptionItemId: string, params: { extendTo: Date }): Promise<BillingSubscriptionItem>
```

## [Parameters](/content/docs/reference/backend/billing/extend-subscription-item-free-trial#parameters/index.html)

- **Name** `subscriptionItemId`  
  **Type** `string`  
  **Description**  
  The ID of the Subscription Item to extend the free trial for.

- **Name** `params`  
  **Type** `{ extendTo: Date; }`  
  **Description**  
  The parameters for the request.

- **Name** `params.extendTo`  
  **Type** `Date`  
  **Description**  
  The date to extend the free trial to. Must be in the future and not more than 365 days from the current trial end date.

## [Usage](/content/docs/reference/backend/billing/extend-subscription-item-free-trial#usage/index.html)

```javascript
const response = await clerkClient.billing.extendSubscriptionItemFreeTrial('subi_123', {
  extendTo: new Date('2026-12-31'),
})
```

## [Backend API (BAPI) endpoint](/content/docs/reference/backend/billing/extend-subscription-item-free-trial#backend-api-bapi-endpoint/index.html)

This method in the SDK is a wrapper around the BAPI endpoint `POST /billing/subscription_items/{subscription_item_id}/extend_free_trial`. See the [BAPI reference](/content/docs/reference/backend-api/tag/billing/POST/billing/subscription_items/%7Bsubscription_item_id%7D/extend_free_trial/index.html) for more information.