This project aims to investigate the pragmatic performance and cognitive processes of candidates taking Aptis General Writing Test (AGWT) Task 4. This task requires candidates to write two transactional emails in different registers to carry out a specific social function. Successful performance in this task requires not only a reasonable level of linguistic competence, but also a fair amount of pragmatic knowledge (i.e. ability to express intended meanings contextually appropriately in social interaction). Against this background, the present project seeks to explore how candidates tap on their pragmatic knowledge to complete AGWT Task 4 and how factors such as first language backgrounds and general language proficiency affect their pragmatic performance. Findings of the project will shed lights on factors in task performance and hence will be useful for both test developers in the process of test validation and localisation and teachers in the process of preparing students for the test.