What is the difference between a deviation and a change control?

Short answer

A deviation records an unexpected departure from an approved instruction, process or specification. Change control evaluates a proposed change before it is made, including its impact on validated conditions and product quality. Both require traceable decisions, but one responds to an event and the other governs a plan.

Why

Start with what triggered the quality workflow. An unplanned excursion, such as a temperature recorded outside an approved limit, must be documented and assessed as a deviation. A proposal to use a different temperature set point is a planned change that belongs in change control.

The deviation investigation establishes what happened, what might be affected and what action is necessary. Change control asks whether the proposed change is justified, how it will affect quality attributes and regulatory commitments, and what verification or revalidation is needed before implementation. The workflows may interact.

A recurring deviation can justify a planned corrective process change, but completing change control does not erase the historical deviation. Site procedures may use more granular terminology. A strong answer stresses clear triggers, risk-based evaluation, approvals and evidence of effectiveness.

A strong answer covers

Distinguish unplanned from planned change
Explain documentation and impact assessment
Acknowledge organization-specific terminology