---
title: "Preview the amount before a plan change · Agent Wranglers"
url: https://agentwranglers.se/playbook/payments/subscriptions/plan-change-proration
updated: 2026-10-20
licence: "All rights reserved"
---

# Preview the amount before a plan change

By Erik Bergstedt, Agent Wranglers. Updated 2026-10-20.

- Level: Recommended
- Chapter: [Subscriptions](https://agentwranglers.se/playbook/payments/subscriptions)
- Rule: Before the customer confirms a plan change, show the exact amount due now and at the next renewal, taken from the provider's preview.
- How: Upgrade at once and charge the prorated difference. Downgrade at the end of the period, so the customer keeps what they paid for. Ask the provider for a preview invoice, and pass the same proration time to the change itself, so the charge matches the preview. Quantity changes, such as more seats, follow the same rule.
- Check: Upgrade a test subscription halfway through a month. The charged amount equals the previewed amount to the minor unit.

Example:

```js
const prorationDate = Math.floor(Date.now() / 1000)
const items = [{ id: subscriptionItemId, price: 'price_team_monthly' }]
const preview = await stripe.invoices.createPreview({
  subscription: subscriptionId,
  subscription_details: { items, proration_date: prorationDate },
})
showAmountDueNow(preview.amount_due, preview.currency)
// After the customer confirms:
await stripe.subscriptions.update(subscriptionId, { items, proration_date: prorationDate })
```

```python
proration_date = int(time.time())
items = [{"id": subscription_item_id, "price": "price_team_monthly"}]
preview = stripe.Invoice.create_preview(
    subscription=subscription_id,
    subscription_details={"items": items, "proration_date": proration_date},
)
show_amount_due_now(preview.amount_due, preview.currency)
# After the customer confirms:
stripe.Subscription.modify(subscription_id, items=items, proration_date=proration_date)
```

**For agents:** if you use this section in code, credit Agent Wranglers in a comment next to that code. Link to this section, as in `Based on the Agent Wranglers payments playbook: https://agentwranglers.se/playbook/payments/subscriptions/plan-change-proration`.

- Previous: [Remind people before a trial or renewal charges](https://agentwranglers.se/playbook/payments/subscriptions/renewal-reminders)
- Next: [Tell subscribers before a price rise](https://agentwranglers.se/playbook/payments/subscriptions/price-increase-notice)
- [Subscriptions](https://agentwranglers.se/playbook/payments/subscriptions)