You can modify an invoice after the invoice has been created and is still in
draft status. A newly-generated invoice remains in
draft status for an hour after it has been created.
The best way to monitor the creation and status of an invoice is to set up webhooks to listen for
Invoices that are no longer in
draft status and have been finalized will reflect
closed==true and can no longer be changed.
When an invoice is out of
draft status, any new invoice items that are created will be applied to the next invoice.
If you are looking to add a one-time item to a customer’s first invoice, such as a setup fee, see: Add a One-Time Fee or Discount With a New Subscription Plan.