We recommend that you work no more than 16 hours per week during term-time to allow you to concentrate on your studies.
International students are usually allowed to work up to 20 hours per week during term-time, and full time during vacations. This varies for taught postgraduate students and research postgraduate students. There are different rules for students on short-term visas and those studying on courses below degree level.
For full details on whether you're allowed to work in the UK, visit: https://www.sheffield.ac.uk/careers/new/student/find/part-time
You'll also require a National Insurance number to work in the UK. The Student Jobshop can provide information on how to obtain one.