A non-conformance means that something went wrong – a problem has occurred and needs to be addressed. Non-conformances are addressed with corrective actions.
You may find a non-conformance in a service, a product, a process, from a supplier, or in the system itself. It occurs when something does not meet the specifications or requirements in some way. Those requirements might be defined by the customer, a regulatory body, or in the internal procedures of the company.
A non-conformance could be identified through customer complaints, internal audits, external audits, incoming material inspection or simply during normal testing and inspection activities.
ISO 9001:2008 requires that you document your non-conformance procedure (clause 8.3) and keep records of non-conformance issues you identify and the actions taken.
ISO 9001:2015 no longer requires a documented procedure, but you must still keep records (“retain documented information”) of the nonconformity and what was done to correct it.
You’ll need to work out a process (documented or not) for how your organisation will deal with nonconforming output: