Should calibration be done during IQ or as part of OQ?

The assignment of the calibration either to IQ or OQ is not clear cut, and in the end it depends on the specific design of the equipment under consideration. While defining and identifying the measuring points and checking the calibration certificates can be assigned to the IQ, the execution of the calibration itself often makes most sense as part of the OQ.

[GMP Compliance Adviser, Chapter 6.E.3]