Under the GDPR, a written agreement between the controller and processor in relation to processing conducted on the controller's behalf must include an obligation on the processor to assist the controller in complying with the controller's obligations to notify the supervisory authority about personal data breaches. This is one of the requirements under Article 28(3)(f) of the GDPR, which specifies the minimum content of such an agreement. The other options are not required by the GDPR, although they may be agreed upon by the parties as additional terms. Reference: GDPR, Article 28(3)(f).