.ES domain owner change
Change the registrant for .ES domains is relatively easy, you only have to follow this steps:
You can make the registrant change for .ES domains from the "Solicitud Transmisión de dominio" you'll find after accessing Nic.es with your Nic-Handle and password (https://www.nic.es/sgnd/login.action?tipoContactoElegido=1&nivelDominio=2 *). In this section you'll be able to write the domain (the actual and new registrant fields will be filled automatically), the registrant and the administrative contact person (PCA)**, write the captcha and press "Continuar".
In the next step you have to sign the request with the DNIe or attach a copy of your ID (it can't exceed 600px wide, if you're having problems attaching it try reducing the size and try again).
Nic.es will ask the actual registrant or administrative contact the acceptance (they send an e-mail to you and you'll have to access with your Nic-Handle to accept the process), once the process has been accepted the registrant change will be started, Nic.es will review the request and if it's all right, they'll accept it. The acceptance period can take up to 5-7 days, but some times the acceptance has been made after a few hours.
In case you didn't accept the request, it will be cancelled automatically after 10 days.
* In case you don't have the password associated to your Nic-Handle you'll be able to recover it from this same link.
** In case you don't have Nic-Handle for the new registrant, you can create one here: https://www.nic.es/sgnd/contacto/publicAltaContactoInicializar.action
*** Note that if you already have a .ES domain you already have a Nic-Handle, you can find it doing a Whois search to your domain.
In case you don't write SCIP (our accreditation) as "Agente Registrador", the domain will be managed directly by Nic.es