What are account recovery codes?

Recovery codes are single-use backup codes a service issues when you turn on multi-factor authentication, so you can still get in if the second factor is gone:

• They are shown once - at setup. Most people click past the screen and never see them again.
• Each works only once - and the set can be regenerated, which invalidates the old set.
• Store them offline - printed, or in a password manager. Not in the mailbox they would let you recover.

Generate a set for your email, your banking and your accounting platform. Those three carry the rest.