Hope you are receiving the leave applications from the employees. In the leave application itself, please add one more column about whether they are planning to avail LTA. If they mention "yes," then you should send an advance note to the Finance Department indicating that these employees are planning to avail LTA and specifying their leave period. For tax benefit purposes, employees are required to submit the original tickets/boarding passes (for air travel) along with their LTA Claim.
Instead of informing all the employees, kindly send an email/note to the Accounts/Finance department, instructing them not to process LTA claim payments without authorization from the HR Department. If they comply, there should be no cause for concern. All employees will seek your authorization for LTA payments.