In he NHS trust I work for, you have to book any annual leave requests onto an electronic system (ESR for those who know it). In my department, there's also a wall calendar (year planner) and every manager also has a paper diary.
There's someone on my team who I know for a fact (they were bragging about it in a non-work related social setting, an activity we both attend with our kids) has NOT been putting all their annual leave on ESR. They add it whenever they are going away for a week or two but if it's just the odd day here and there, they don't add it. They were saying they get round it by saying "I'll add it later, system's a bit slow at the moment or some IT problem".
They've worked on the team for nearly 3 years so I imagine they've had a lot of unofficial annual leave. They declare on the wall planner and through emails to manager but don't actually record it on ESR.
How can this go unchecked for so long?