Sign in, go to /app/account, and click Delete my account. You'll be asked to confirm twice.
Within 30 days your profile, remaining minutes, usage history, and settings are permanently removed from our database. Order history is kept for 7 years for tax reasons, with your email redacted.
Your audio and transcript files on your Mac are NOT deleted by this action — they live on your local disk. Move them to Trash manually if you want them gone.