ISO 14001 is the specification standard. It is the standard that companies will implement and the standard to which your business will either self-declare conformance or seek third-party certification. ISO 14001 contains only those requirements that may be objectively audited against for registration purposes and/or self-declaration purposes.

ISO 14004 is a guidance standard. It offers useful guidance in the form of examples and descriptions related to the development and implementation of an EMS. Although ISO 14001 and ISO 14004 share key concepts and definitions, ISO 14004 is intended for use as a voluntary, internal management tool and not for use by EMS certification bodies as a specification standard.

The ISO 14010-14012 series are guidance, not specification standards. They offer useful advice but are not designed for third-party registration of a your company's auditing procedures.