Here are the differences (from FDA’s guide):
In terms of definitions:
QA – Proactive and retrospective activities that provide confidence that requirements are fulfilled
QC– The steps taken during the generation of a product or service to ensure that it meets requirements and that the product or service is reproducible
In terms of functions:
QC usually involves (1) assessing the suitability of incoming components, containers, closures, labeling, in-process materials, and the finished products; (2) evaluating the performance of the manufacturing process to ensure adherence to proper specifications and limits; and (3) determining the acceptability of each batch for release.
QA primarily involves (1) review and approval of all procedures related to production and maintenance, (2) review of associated records, and (3) auditing and performing/evaluating trend analyses.