Getting certified to a standard means that an independent third party, called a Certification Body (CB), has assessed and approved your compliance to ISO 14001 standard. Monitoring or checking the implemented system is an important part of the ISO 14001 standard. Alternatively, you may invite your clients to audit the environmental management systems themselves, which is known as a second-party audit. So, while certification to the ISO 14001 standard is not mandatory, it can be a helpful way to show that you meet its requirements.