Reduced Testing a Matter of GMP or Specification?

The European Medicines Agency (EMA) has published an updated version of its 'Quality of Medicines: Questions and Answers - Part 2'.
EMA clarifies that reduced incoming testing of starting materials is a GMP issue and should not form part of the specifications described in the marketing authorisation dossier. The agency says that "although some parameters should always be tested on receipt by the finished product manufacturer, such as identification and specific requirements for excipients with an identified risk (e.g., diethylene glycol/ethylene glycol contamination), what is actually tested on receipt is covered under good manufacturing practice [for human medicinal products: EU GMP part I, chapter 5 (5.27 to 5.39), for veterinary medicinal products: Commission Implementing Regulation (EU) 2025/2091, Article 28].
Consequently, the relevant registered specifications for incoming starting materials used by the finished product manufacturer in the marketing authorisation application should not include any reference at all to reduced testing of said materials."

EMA points out that reduced testing should not be confused with skip testing.

Skip (or periodic) testing, as described in ICH Q6A / VICH GL 39, means performing certain release tests only on "pre-selected batches" and/or at "predetermined intervals", instead of testing every batch.
ICH Q6A / VICH GL 39 requires that skip testing is "comprehensively justified", supported by appropriate data. It also needs to be "approved by the competent authority(ies)" responsible for assessing the dossier.

While the guideline indicates that skip testing is generally introduced after approval, when more manufacturing and testing data are available, it may also be accepted at the time of Marketing Authorisation Application (MAA) submission if the conditions in relevant (V)ICH or EU guidance are met.

Any parameter subject to skip testing should be "clearly indicated in the specification (for example, with an asterisk) and accompanied by a footnote stating the testing frequency."