We've updated the billing system for your OpenAI API account. Instead of receiving a bill at the end of the month, you'll now need to pre-purchase credits to use the API. You can add credits to your account by visiting the billing page. To learn more about prepaid billing, please see this help center article prepaid billing.
No action is required from you at this time.
Please note that this change only applies to your OpenAI API account and Playground. It does not affect ChatGPT Plus subscriptions.
Best, The OpenAI team