Abstract: The invention relates to a document of value, a security element and a security marking that have a marking substance absorbing in the infrared spectral region between 1000 and 2500 nanometers which does not significantly absorb either in the visible spectral region or at 800 nanometers. Said marking substance is therefore not accessible with the widespread, simple IR readers working at about 800 nanometers. Preferably, an additional print is added that absorbs in the visible and also at about 800 nanometers but not in the range from 1000 to 2500 nanometers. According to the inventive checking method, the marked place is irradiated with infrared light from the range from 1000 to 2500 nanometers and the absorption determined.