Can unused leave be carried over?
Carry-over is an employer policy decision, and quotas here are set per leave type per year. A balance moving from one year into the next is written into the new year's allocation by an administrator, following the company's own rule, so every carried day is visible in the grid.
A year boundary is where most leave systems quietly part company with the policy they are meant to follow.
Three schemes are common, and they behave very differently. Nothing carries. A capped number carries. Anything carried has to be used by a stated date.
A product picking one of those would be wrong for the other two. So the grid holds whatever figure a company decides, and works none of it out.
That puts the job somewhere specific. Better than a rule nobody wrote down, applied two different ways by two people.
The year selector makes the two periods readable side by side, which is what the check needs. What it does not do is move a number between them.
So the check is a manual one, and it is quick. Set the new year's figures, then read last year's row next to them. A few minutes in January prevents an argument in February.
Different types can behave differently, and usually should. Nothing forces one rule across all of them. A firm can let a holiday allowance roll forward while an emergency one does not.
Write the rule and the date it bites into the leave policy. A rule that lives only inside a yearly calculation gets done slightly differently by whoever does it next.
Nothing expires on its own here either. Whatever the new year's cell holds is what the new year holds.
Where a policy allows carry-over, the year selector makes the two periods readable side by side. What it does not do is move a figure between them.
Write down the carry-over rule and the date it bites, then check the allocations at the year boundary. That check takes minutes and prevents an argument in February.
Related questions
Does anything expire automatically?
Days follow the allocation. Whatever the administrator sets for the new year is what the new year holds, so an expiry rule is applied when those figures are set.
Where is the rule written?
In the employer's own leave policy, which sits in the published policy set. The policy is the source; the allocation grid is the implementation.
Can different types carry differently?
Quotas are per type, so nothing forces one rule across all of them. A company can treat annual and casual allowances differently.