Security document (1) that has a transparent window (2) and a UV- absorbing security element (3) in it, characterised by that the UV- absorbing security element (3) is located on a part of the area of the transparent window (2), and the UV-absorbing security element (3) is an element containing UV-absorbing ink. System for checking the security document (1), characterised by that it contains a UV light source (4), a security document (1) and a UV fluorescent surface (6), where the security document (1) is located between the UV light source (4) and the UV fluorescent surface (6), and where the UV light source (4) illuminates the UV fluorescent surface (6) through the transparent window (2), and the UV-absorbing security element (3) projects a shadow (5) onto the UV fluorescent surface (6).