> ## Documentation Index
> Fetch the complete documentation index at: https://docs.getlago.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Upgrades and downgrades

> Customers have the flexibility to easily upgrade or downgrade their plan at any given moment.

<Tabs>
  <Tab title="Dashboard">
    To perform an upgrade or a downgrade through the user interface:

    1. Access the **"Customers"** section via the side menu;
    2. Select a customer from the list;
    3. In the **"Overview"** tab. By clicking the ellipsis icon, you can **"Upgrade/downgrade plan"**;
    4. Give a name to the new subscription (name that will be displayed on the invoice - optional);
    5. Provide a new subscription end date if needed (optional);
    6. Click **"Upgrade/downgrade plan"** to confirm.
  </Tab>

  <Tab title="API">
    <CodeGroup>
      ```bash Upgrade or downgrade a subscription theme={"dark"}
      curl --request POST \
      --url https://api.getlago.com/api/v1/subscriptions \
      --header 'Authorization: Bearer <bearer>' \
      --data '{
        "subscription": {
            "external_customer_id": "5eb02857-a71e-4ea2-bcf9-57d3a41bc6ba",
            "plan_code": "new_plan",
            "external_id": "existing_sub_id"
          }
        }'
      ```
    </CodeGroup>
  </Tab>
</Tabs>

## Upgrades behavior

An upgrade occurs when the subscription fee of the new plan, calculated on a daily basis, equals or exceeds the subscription fee of the previous plan,
regardless of the pricing for usage-based charges.

When a subscription is upgraded, Lago immediately applies the new plan to the customer.

### Subscription paid in advance

Lago issues a [credit note](/guide/invoicing/credit-notes/overview) for the unused days remaining on the former plan.

### Subscription paid in arrears

When a plan is upgraded mid-cycle, Lago immediately generates an invoice covering the prorated portion of the old plan (i.e., the days used before the upgrade).
At the end of the billing period, a second invoice is issued for the prorated portion of the new plan (i.e., the days used after the upgrade).

**Example:** A customer subscribes to Plan A (€100/month, paid in arrears, calendar billing) on January 1st, then upgrades to Plan B (€200/month) on January 15th.

* **January 15th** — Invoice for Plan A: 14 days prorated = **€45.16** (14/31 × €100)
* **January 31st** — Invoice for Plan B: 17 days prorated = **€109.68** (17/31 × €200)

## Downgrades behavior

A downgrade occurs when the subscription fee of the new plan, calculated on a daily basis is lower than the subscription fee of the previous plan,
regardless of the pricing for usage-based charges.

When a subscription is downgraded:

* The new plan is applied at the end of the current billing period to ensure that your customer fully benefits from the plan they have already paid for. The newly applied plan will be in a pending state.

## Webhook messages for upgrades and downgrades

When a subscription is upgraded or downgraded:

* A `subscription.terminated` webhook message is triggered for the initial plan, with a `next_plan_code` defined in the payload;
* A `subscription.started` webhook message is triggered for the new plan, with a `previous_plan_code` defined in the payload;
* The `subscription.external_id` is persisted between the two to ensure the continuity of the subscription.