What term describes assurance that a product or service will meet its agreed requirements?

An underpinning contract is an agreement between a service provider and an external third-party supplier that supports delivery of a service, not the direct assurance mechanism for customer requirements.

Warranty in ITIL refers specifically to fitness for use - assurance around availability, continuity, security, and capacity dimensions - rather than the broader formal record of all agreed service requirements.

A service level agreement (SLA) is a documented agreement between a service provider and a customer that specifies service targets, responsibilities, and measurable performance criteria, providing formal assurance that the service will meet its agreed requirements. The SLA functions as the binding assurance mechanism that holds the provider accountable to defined commitments. It translates customer expectations into quantifiable, enforceable service obligations.

Utility describes the functionality a service provides to meet a particular need (fitness for purpose), which is the 'what' the service does rather than the assurance it will meet requirements.