Though your post is short, something like SMS, it raises a question in the mind of a reader whether you have proper policy on employee leave and if yes, then whether it has been circulated and if it has been circulated then whether the staff have understood it.
While drafting policy on employee, entire process of how employees should avail of their leave is enumerated. Additional points that this policy covers is the types of leave, admissibility, who will maintain the records etc.
When employees go on leave, they come back and resume their duties but forward application to HR at the end of the month then it appears that basic HR process is missing. Therefore, if the malaise lies in improper policy then you need to fix it. The malaise cannot be eradicated by mere issue of the office circular.