Some students do sit more than one exam in a day, but you do have to be really confident in both subjects, otherwise you risk failing both.

There are some exams that have to be sat in order:

At Level 2 it is PBKT followed by CJBS and Level 3 APCP followed by FSTP. Otherwise you can sit in any order.

If you are contemplating sitting two try to pair up a large and small unit. For example CJBS with Basic Costing.