If you want to study in the UK, you need to be familiar with a document called a Confirmation of Acceptance for Studies, or CAS for short. CAS is a significant piece of paper regarding study in the UK.
If you plan on attending university in the UK, you will need a CAS. You won't be able to enroll at a UK university without a current CAS. There is a basic explanation of CAS provided by SMS-HEG here.
After accepting an offer of admission and paying the payment to secure your spot at the university, you will be given a CAS letter confirming your enrollment. It includes information such as the student's personal details, the program that the student has chosen, the duration of the program, as well as a unique CAS number. You will only receive this letter once you have satisfied the specified academic and financial conditions. Additionally, you may be required to submit an acceptance form, pay the acceptance fee, and finish a pre-CAS procedure.
The conventions established by UK immigration require that the university sponsor the student's application for a student visa. As a result, a CAS number is necessary. This number verifies that the student has accepted the university's offer, which was given without any attached conditions.
Before applying to a UK Student Visa (Tier 4 General), you must first obtain a CAS. Your college or university will provide you with an electronic CAS. After the date it was issued, your CAS will be valid for six months when applying for a student visa. There aren't that many schools in the UK that will require you to apply for a CAS number, even though many universities in the UK will send the CAS letter.
In addition, the sending institution will provide a one-of-a-kind reference number that will correlate with your CAS. You are required to note this reference number on the application form for the Tier 4 visa. The official in charge of processing your visa application will check this number and any supporting documentation to verify that you have been extended an unconditional offer from the university.
In contrast, your college's information to compile your CAS will be forwarded to you. You will receive this document, referred to as a "CAS statement," through email. The CAS statement is not required for you to apply for a Tier 4 visa; however, it does provide all of the information about your course and sponsor, in addition to some information about the amount of money you will need, so that you may finish your Tier 4 visa application form.
Your application for a visa may be denied if there are discrepancies between the information that the university used to construct the CAS and the information you supply on your application form.