Leave application and approval Process in the office - via HR to the reporting Authority or boss, or should it be the other way around?

Dear Seniors, I want to understand the details of the leave process.
1 -Leaves for 1 day or more, like 10 days, should be approved by their Manager/supervisor or HR?
2- Does the Leave application go via HR to the reporting Authority or boss, or should it be the other way around?
3- Should the leave application be verbally discussed(reasoning and approval) first, and then a formal application should be given, or should it be applied first to the HR and Manager and then will be discussed?

Thanks in advance.

Hi,

In normal course the leaves are to be approved by immediate Superior /Head of the Department. Employee can directly get the leave approved from the immediate supervisor and no need to route through HR. Generally employees should discuss with their immediate superior about their leave requirement and then leave card updation and approval process will take place. This is applicable for planned leave only. For unplanned leaves employee should update the superior on the day of leave itself wherever possible. Only in case of leave requirement beyond 10 days or so HR should be involved to discuss the reason.