As recorded at collection: Codex friend referral, 500 usage limit for both parties

When a Codex friend referral is successful, each account receives a usage limit of 500. The poster says the usage limit arrived within a few minutes after the referral succeeded.

Open Codex and tap the profile picture in the lower left to find the friend referral menu. If a green reward notice appears on the referral page, you are eligible to invite friends. Enter your friend's email in the field and tap send. Your friend must open the official referral email, sign in to their own account, then complete the steps shown on the page in the ChatGPT desktop version. There is also guidance saying that sellers on secondhand marketplaces will explain how to use it if you place an order with them.

Sending an email alone does not grant a reward. After your friend completes the steps, tap Track invitations in the referral center to check whether the invitation was accepted. When the reward is granted, both accounts will display a reward notification, and you can check the balance under usage. The reward amount, number of invitations allowed, and eligibility may vary by account, so follow the information shown on your own referral page. If the referral menu itself is missing, the referral feature is currently unavailable.