Support different Leave Periods per Leave Type

[dvdl16]

Is your feature request related to a problem? Please describe.

ERPNext currently assumes that all Leave Types operate within the same Leave Period. This creates limitations when different types of leave follow different time-based rules.

For example:

• Annual leave typically resets every year
• Sick leave may accumulate over multiple years (e.g. a rolling 3-year cycle)

Because the Leave Period is shared across all leave types, it becomes difficult to model these policies correctly without workarounds. This leads to:

• Incorrect enforcement of allocation limits
• Loss of control when using overrides like “Allow Over Allocation”
• Manual tracking outside the system in more complex cases

Describe the solution you'd like

Allow Leave Period to be defined per Leave Type instead of globally.

Possible implementation:

• Add an optional Leave Period field on Leave Type
• If set, it overrides the global Leave Period
• If not set, the system falls back to the existing global Leave Period

This would allow:

• Annual Leave: yearly Leave Period
• Sick Leave: multi-year Leave Period
• Other leave types: custom-defined periods as needed

Describe the alternatives you've considered

• Setting “Maximum Leave Allocation Allowed per Leave Period” to unlimited
• Enabling “Allow Over Allocation”

These bypass the limitation but reduce control and introduce risk of incorrect allocations.

Additional context

A related issue with similar flexibility limitations is #4225

That issue is more about multiple components within a single leave allocation, this is for allowing different time boundaries per leave type.