How can I propagate custom fields from a Stripe Checkout session to a finalized invoice?

Unfortunately, there isn’t a way to have custom fields from Checkout automatically propagate to the invoice once it’s finalized. When you use Stripe Checkout with automatic collection, the invoice is finalized (and thus locked from editing) as part of the hosted flow, so you can’t later update it via the webhook after the checkout session completion.

To summarize:

• With the hosted Checkout flow that uses automatic charges, Stripe finalizes the invoice automatically (after a short delay) and attempts payment.
• Since the invoice is finalized by the time the checkout session’s webhook fires, you can’t update it with custom field data.
• Currently, there’s no built-in configuration or API option to delay invoice finalization solely for the purpose of adding custom fields.

If having those custom fields on the invoice is crucial, you might consider one of the following workarounds:

1. Leverage manual invoice workflows:
   Instead of using automatic charges with Checkout, you could use an approach where the invoice is created in draft state. You’d collect the custom fields during the Checkout session, update the draft invoice accordingly, and then finalize and pay it manually. However, this requires additional plumbing.

2. Custom integration using Payment Intents:
   Although not ideal if you want to avoid building your own checkout flow, a direct integration with Payment Intents can give you the control needed to delay invoice finalization. This would let you modify the invoice (for example, adding custom fields) before charging the customer.

We understand that these workarounds might not be as straightforward as a native solution within Checkout. Currently, the hosted Checkout experience is designed to streamline payment and invoicing processes, which limits the ability to inject custom logic into the invoice finalization step.

If you have more questions or need further assistance, please let us know.