Additional requirements when employing a Student/ Tier 4 visa holder
Most undergraduate and taught postgraduate students on Student/ Tier 4 visas are restricted to a maximum of 20 hours per week work during term-time. Any time during which students have study commitments (this includes any weeks when the student has study commitments, even if this is outside of the standard term-time) is also included in this restriction. Paid and unpaid work count towards the student's maximum permitted working hours.
Most postgraduate research students on Student/ Tier 4 visas are restricted to a maximum of 20 hours per week of work throughout the year, since research students are not considered to have terms.
In addition to a right to work check, you will need to also complete a Tier 4 Student Employment Declaration.
Further information may be found here