Confirmation of Acceptance to Study (CAS) is another important requirement for studying in the UK.  Without this letter, students cannot apply for a student visa.  The CAS letter is issued by the selected university/institution after students have submitted an unconditional offer letter.  This is a comprehensive letter that is issued electronically and is issued on a first-come, first-served basis.  It contains a unique license number that indicates that the university has accepted your application and invited you to study at its institution.