<p>Specifies the 12 digit account ID number of the Amazon Web Services account that you want to access or modify with this operation.</p> <p>If you do not specify this parameter, it defaults to the Amazon Web Services account of the identity used to call the operation.</p> <p>To use this parameter, the caller must be an identity in the <a href="https://docs.aws.amazon.com/organizations/latest/userguide/orgs_getting-started_concepts.html#account">organization's management account</a> or a delegated administrator account, and the specified account ID must be a member account in the same organization. The organization must have <a href="https://docs.aws.amazon.com/organizations/latest/userguide/orgs_manage_org_support-all-features.html">all features enabled</a>, and the organization must have <a href="https://docs.aws.amazon.com/organizations/latest/userguide/services-that-can-integrate-account.html">trusted access</a> enabled for the Account Management service, and optionally a <a href="https://docs.aws.amazon.com/organizations/latest/userguide/orgs_getting-started_concepts.html#delegated-admin">delegated administrator</a> account assigned.</p> <note> <p>The management account can't specify its own <code>AccountId</code>; it must call the operation in standalone context by not including the <code>AccountId</code> parameter.</p> </note> <p>To call this operation on an account that is not a member of an organization, then don't specify this parameter, and call the operation using an identity belonging to the account whose contacts you wish to retrieve or modify.</p>