Time management is crucial for academic success, particularly in higher education, where deadlines play a significant role. While students recognise the importance of assignments, they often struggle due to several reasons. This study aims to examine the online submission behaviours of undergraduate EFL students and explore the reasons behind last-minute submissions. The relationship between last-minute submissions and initiation types (time), academic performance, and variation among different deadline hours were examined through quantitative methods and the factors affecting the participants’ behaviours were explored through qualitative methods. Quantitative results shed light on when and how participants submit assignments and illustrates that last-minute submissions occurred regardless of initiation type, and submission timing didn't impact academic performance. Qualitative results showed that many factors such as strategical planning, the complexity of the assignment, anxiety, physical health, procrastination, academic overload, household environment, and access to technology affect the submission behaviours. In light of these results, implications regarding coping with anxiety and procrastination are recommended in the conclusion.