t4签证为什么只给三个月？
T4-General学生类（普通学生课程）是英国政府为海外留学生专门设立的以工作或学习为目的签证类型，与T1-T5其他签证类别不同，不限制留学生的资金来源和移民目的。 然而，2016年7月15日起实施的新的学生签政策规定所有申请T4的学生签证申请人必须首先获得一个CAS号码才能提出申请。这个CAS号码将表明申请者被某个特定的学校录取，专业名称及入学时间等信息。 T4-General学生类分三种情况如下：
1. 本科及硕士(包括授课式和研究式)全日制学生；本科生最长可获3年的有效期签证，硕士生可获得两年有效期的签证；
2. 博士全日制学生；可获得为期三年的有效期的签证；
3. 在英国就读的短期的语言培训及非全日制的学生；最短可达六个月，最高不超过一年; 注意：在英语授课的国际大学中，有极少部分专业开设一年制的硕士学位课程，这类课程的毕业生不能取得T4学生签证。因为根据新规定，在英国攻读研究生及以上课程不能超过一年！
Tier 4 is for overseas students who want to study a course in England and Wales that has been approved by the Home Office under Tier 4 (higher education) of the Points Based System， or on an undergraduate degree at university which is not otherwise tier four approved but where it can be reasonably expected there will be no more than five students from outside Europe studying the same programme as you are， and your course starts this academic year or soon afterwards． Students must have secured a Confirmation of Acceptance for Studies (CAS No.) before they apply．This number is issued by their UK higher education provider after receiving an offer of a place on a course. The CAS Number includes details of the student's name， date of birth， passport number etc.，as well as information about the institution that has offered them a place such as its name， address and the course being taken· This makes it much harder for students to switch from one college to another if things don’t go according to plan. It also means that a change of course will require the application of a whole new visa process with all associated fees – so it’s definitely worth checking out whether any changes might affect how long your course lasts！
The main requirements for Tier 4 visas include：
You should check the list of documents required when applying for Tier 4 visa. And remember： If you provide false details， your visa application may be refused and/or you could face criminal prosecution！ Also important note here： You need to prove that your funds are genuine and are available through legally obtained sources，