The GMP+ exam is a theoretic test to determine whether GMP+ auditors have the required knowledge. Succefully completing a GMP+ exam is a required element for auditors in obtaining and maintaining GMP+ acceptance.
In addition to the exam, there also is a documentation duty. This is verified and inspected annually by the Certification Bodies with GMP+ International. The exact requirements are documented in annex 2 of the GMP+ C10 Acceptance requirements and Procedure for Certification Bodies.
Certification Bodies that have not (yet) been accepted by GMP+ International can still sign up their auditors for the GMP+ exam.