This isn't a hypothetical. We recently covered a four-month leave for a company's sole People person, handling payroll and HRIS administration, 401k administration, and benefits compliance for the duration. Here's what that kind of handoff actually needs to cover, based on doing it.
Why this is harder than it looks
The instinct is to treat this like any other handoff: write some notes, forward some logins, done in an afternoon. People ops doesn't work that way, because the failure modes aren't visible until they happen. Payroll runs on a fixed schedule with real deadlines, miss one and people don't get paid on time. Benefits compliance has filing windows that don't pause for someone's leave. A retirement plan administrator needs a specific person authorized to approve transactions, and that authorization doesn't transfer itself.
The company's instinct is usually to ask "who can just handle this for a few months," without realizing the honest answer requires someone who already knows payroll systems, benefits administration, and compliance, not someone learning it during the gap.
What the handoff needs to cover
System access, documented and tested before day one of the leave, not during it. Every system the role touches (payroll/HRIS, retirement plan administration, benefits portals, any compliance filing tools) needs a named, authorized backup with access confirmed working, not just granted. Access that was "set up" but never tested is the failure we hit first, in week one.
A payroll run calendar with every non-obvious step written down. Not "run payroll on the 15th and 30th," but the specific manual adjustments, approval steps, and quirks that live only in the departing person's head. If there's a standing exception (a contractor paid differently, a benefit deduction that doesn't automate cleanly), it needs to be written down explicitly, because it will come up during the leave and nobody else will know to look for it.
Retirement plan administration authority, set up in advance. Who can approve enrollment changes, loan requests, or distributions while the primary person is out. This usually requires a specific authorization step with the plan provider that takes time to process, so it has to happen weeks before the leave starts, not the week of.
A compliance calendar for the leave window specifically. Filing deadlines, open enrollment windows, and renewal dates that fall during the leave period, flagged in advance with enough lead time to actually prepare for each one, not discovered the week they're due.
One clear point of contact for employees. During a leave like this, employees still have benefits questions, payroll issues, and HR concerns. Ambiguity about who to go to erodes trust fast. Name the person explicitly and communicate it before the leave starts, not after the first question goes unanswered.
A defined re-entry plan. What's been decided in the person's absence that they need to be briefed on, and what's been deliberately held for their return. Without this, the first two weeks back get spent reconstructing four months of context instead of actually transitioning back in.
What breaks when this isn't planned
The risk isn't abstract. A missed payroll deadline means employees don't get paid correctly, which is a trust problem that outlasts the leave itself. A missed compliance filing can mean penalties. A retirement plan transaction that nobody was authorized to approve means an employee's loan or distribution sits stuck for weeks. None of these are dramatic failures on their own, but they compound, and they land during a period when the company has already lost its most experienced person in this function.