AWS account should be part of an AWS Organizations organization

How to fix it

Bring this account under an AWS Organizations organization. The usual route is an invitation from the management account of an organization you already have, accepted by an administrator here, so this is not a change this account can make alone. Creating an organization here instead makes this account its management account, which is the harder end state to reverse. Either way billing consolidates to the management account and the organization's service control policies start applying here.

In the console

AWS Organizations → Create an organization, or, from the management account, AWS Organizations → AWS accounts → Add an AWS account