Validation requirements apply to all medical device software regardless of its class or whether it is a software component or itself a medical device. Software validation should confirm that software specifications meet user needs and intended uses, and requirements can be consistently fulfilled. A software validation plan and procedure are required to outline and govern validation activities to develop confidence the device meets all user requirements. Since small changes can impact the system, validation status must be re-established after any change through appropriate regression testing to ensure no adverse effects. While off-the-shelf software validation can be difficult, the device manufacturer is responsible for compliance with FDA validation requirements through vendor verification and auditing design methodologies.