Comparison between our X-shooter spectrum of Neptune (blue) and the corresponding IRTF reference spectrum (purple) with residuals below. Our spectrum shows a systematically lower flux as it progresses into the infrared, which we attribute to the presence of clouds during the observations. Regions of strong (dark gray) and moderate (light gray) telluric absorption are indicated. These regions were not reliably corrected by MOLECFIT and are flagged as less trustworthy.