To file your tax statements online you can authorize a certified Accountant as follows:
Visit the General Secretariat for Information Systems website (GSIS) www.gsis.gr. Select "Services for Citizens" or "Services for Businesses" and then "Authorizations" and follow the directions provided by the system.
Physical persons may authorize a certified Accountant. It is not necessary for the person authorizing a certified Accountant to notify the access codes or the authenticator key to the Accountant because following the authorization, the Accountant may file all the tax payer's statements using his codes.
Following the authorization, the Accountant must accept the authorization in order to be able to act on behalf of the tax payer only regarding online services covered by the authorization. The tax payer may revoke online the authorization of the Accountant for any reason following the same process as during authorization and the revocation of the authorization is sent to the Accountant via e-mail.