While for most X-ray absorption experiments a linear correction of the energy scale is sufficient to calibrate the spectra, in this section the limitations of this approach are discussed, in particular for the case where data are collected over an extended energy range. A selection of options that can be adopted to enhance the accuracy of the energy scale for spectral data are reviewed. The need for a database of reference metal foil spectra collected with high energy accuracy is highlighted. Such a database allows a multi-energy calibration of experimental data for experiments where a linear correction extrapolated from a single energy point is not sufficient. A section is devoted to discussion of energy calibration for data collected using a dispersive spectrometer, and also addresses some of the difficulties that the lower resolution of dispersive-mode data introduces into the task of accurate energy calibration.