Spectrophotometers allow measurement of the optical properties of materials such as transmittance or reflectance. They are used in many industrial fields: health, transport, energy. . . To ensure the traceability of the measurements through the calibration of transmittance and reflectance standards, the LNE uses spectrophotometers that are qualified along the lifetime of these instruments. We present the qualification steps. The results are used to evaluate the uncertainties. The procedure followed can be used as a guideline for spectrophotometer users who want to evaluate their measurement uncertainties.