For a subscription product to prorate, prorate needs to be enabled in the associated plan product in the catalog.
To enable prorate:
- Navigate to Catalog >Plans. Click a plan and click a plan product.

- Scroll down to the Pricing block, select the timing option from the Advanced Setting column and click Go.

- Select Prorate and click Save.

Note: These changes will not affect existing subscriptions. It will only affect new subscriptions moving forward.