> For the complete documentation index, see [llms.txt](https://developer.paddle.com/llms.txt).

# Update trialing subscriptions

Add or remove recurring items, change quantities, bill for one-time charges, and change the next billing date for subscriptions in trial.

---

## What's new?

You can now update trialing subscriptions, including:

* Adding or removing items
* Changing quantities
* Billing for one-time charges
* Changing the next billing date

There are no changes to endpoints or fields in the API as a result of this change — it's an update to the way the Paddle platform handles trialing subscriptions.

## How it works

Previously, you couldn't make changes to a trialing subscription. We updated the Paddle platform so now you can add or remove items, change quantities, bill for one-time charges, and change the next billing date. This lets you do things like:

* [Upgrade or downgrade a plan](https://developer.paddle.com/build/subscriptions/replace-products-prices-upgrade-downgrade.md)
* [Add or remove addons or additional modules](https://developer.paddle.com/build/subscriptions/add-remove-products-prices-addons.md)
* [Extend or cut short a trial](https://developer.paddle.com/build/subscriptions/extend-activate-change-date-trials.md) by changing the next billing date
* [Bill for charges or fees](https://developer.paddle.com/build/subscriptions/bill-add-one-time-charge.md), like importing or setup

You might let customers make changes to their subscription as part of a workflow where they confirm and activate their subscription, transitioning to a paid plan.

{% callout type="info" %}
Proration doesn't apply to updates made to a subscription that's in trial. You must use `do_not_bill` as the `proration_billing_mode` when sending requests.
{% /callout %}

{% accordion %}
{% accordion-item title="Full list of updatable fields" %}

Here's a list of the fields you can update where a subscription `status` is `trialing`:

- **subscription** (object): Represents a subscription entity.
  - **items** (array): List of items on this subscription. Only recurring items may be added. Send the complete list of items that should be on this subscription, including existing items to retain.
  - **next_billed_at** (string): RFC 3339 datetime string of when this subscription is next scheduled to be billed. Include to change the next billing date.

{% /accordion-item %}
{% /accordion %}

### Changes to error messages

This change is an update to the way the Paddle platform handles trialing subscriptions. Error messages are the same, but may be returned in different circumstances:

* The [`subscription_update_when_trialing`](https://developer.paddle.com/errors/subscriptions/subscription_update_when_trialing.md) error message is no longer returned when adding or removing items, changing item quantities, billing for one-time charges, or changing the next billing date for trialing subscriptions. It's still returned when making other changes to trialing subscriptions.
* The [`subscription_trialing_items_update_invalid_options`](https://developer.paddle.com/errors/subscriptions/subscription_trialing_items_update_invalid_options.md) error message is returned when adding or removing items from a trialing subscription when the `proration_billing_mode` is a value other than `do_not_bill`.

## Next steps

This change is available in version `1` of the Paddle API.

It's a non-breaking change, meaning it doesn't impact existing integrations.

Check out our [work with trials guide](https://developer.paddle.com/build/subscriptions/update-trials.md) to get started.
## Summary of changes

| Name | Type | Change | Entity | Description |
| --- | --- | --- | --- | --- |
| `subscription_trialing_items_update_invalid_options` | Error | added | Subscriptions | Returned when proration_billing_mode is not do_not_bill for item changes while trialing. |