# Simulate subscriptions

Learn how to simulate subscriptions in a sandbox.

Simulating a subscription shows you the events of a subscription, such as invoices and renewals, that are expected over the course of the simulation time.

> When you run a simulation on a subscription, it appears in the **Simulations** tab of the Subscriptions page. You can delete it by clicking **Finish simulation**. Finishing a simulation deletes all objects associated with it, including the customer and subscription, from the *sandbox* (A sandbox is an isolated test environment that allows you to test Stripe functionality in your account without affecting your live integration. Use sandboxes to safely experiment with new features and changes). It doesn’t affect live mode.

To simulate a subscription:

1. Open the Dashboard and create a sandbox.
1. In the [subscriptions](https://dashboard.stripe.com/test/subscriptions) page, click the subscription to test.
1. Click **Run simulation** in the banner at the top of the page.
   > #### Customer ineligible for simulation
   > 
   > The **Run simulation** button might be disabled if the subscription’s customer:
   > 
   > - Is attached to more than three subscriptions, including [scheduled subscriptions](https://docs.stripe.com/billing/subscriptions/subscription-schedules.md)
   - Has a complex profile, with many quotes, invoices or other related objects
1. In the modal, set the date and time to simulate and click **Advance time**.

You can advance time by any increment, but you can only advance the clock two intervals at a time from the initial frozen time. For example, if you have a monthly subscription, you can only advance the clock up to two months at a time.

When the simulation is done, the banner updates and displays the current time.

You can continue to make changes to your simulation and advance the time for simulations like:

- Adding a [customer balance](https://docs.stripe.com/billing/customer/balance.md).
- Making a mid-cycle upgrade.
- [Adding one-off invoice items](https://docs.stripe.com/billing/invoices/subscription.md#adding-upcoming-invoice-items).

Repeat as many times as you need to satisfy your test case.