.AT is an open registry; you do not have to be an Austrian resident or business operator to register a .AT domain.
Registration details can be found in the TLD reference chart.
.AT domains renew automatically. A domain must be cancelled 3 days before the expiry date to avoid renewal.
If the registrant is an organization, a company stamp must be affixed to the form in the area labeled Company Chop.
Important: There is no refund when you cancel a .AT name. The cancellation must be processed at least 3 days prior to expiry, otherwise the domain will be auto-renewed by the registry.
Registrar to registrar transfers require auth codes. The auth code is set by the sponsoring registrar and is foreseen for the domain holder only who can at any time ask his registrar for the AuthInfo. With this AuthInfo a domain holder can transfer his domain to any ISP/registrar.
For more information on transfers, see "Transferring domains and changing domain ownership"