What is the difference between verification and calibration?

Calibration (VIM 2.39) establishes the relation between the values of standards and the indications of your instrument — with uncertainties. Its output is data: errors/corrections and their uncertainty.

Verification (VIM 2.44) is a pass/fail attestation that the instrument meets a specified requirement, usually that errors are within ±MPE.

A verification is normally based on calibration data — you compare the observed errors (plus their uncertainty, per your decision rule) with the tolerance. So: calibration produces the relation; verification is the conformity decision layered on top. An instrument can be calibrated without being verified (no spec involved), and a verification without underlying measurement against standards isn't metrologically meaningful.

Practical tip for the auditor: make your procedures say 'calibrate, then verify against MPE using decision rule X (ILAC-G8)'.