Reworking: 1) Before a decision is taken to rework batches that do not conform to established standards or specifications, an investigation into the reason for nonconformity is performed. 2) Batches that have been reworked are subjected to appropriate evaluation, testing, stability testing if warranted, and documentation to show that the reworked product is of equivalent quality to that produced by the original process. Rework procedure is validated concurrently.