01 · The problem
The checklist isn't the problem.
You already have one — a spreadsheet, or a template baked into your close software. Keep it. A list is a record: it tells you the intercompany rec is outstanding, but it can't ask the person who owns it and it doesn't notice the FX reval is late. That has always been a human job, done by hand at the worst point in the month.
02 · What you need
“Reconciled” isn't a checkbox until the ledger agrees.
Where a close line is linked to a tracked task, she checks it actually closed there before marking the line done — instead of taking a "posted" message at its word. Where a line isn't linked, she holds it and tells you it's on someone's say-so. She never dresses up an unverified line as confirmed.
03 · How it runs
Set the close once; it reopens every month.
Set where the asking happens and what a line gets checked against. Every step rewrites itself to match — you're not rebuilding the checklist, you're handing off the part where you nag, and every chase has a point where it stops and reports the gap to you.
04 · What it's worth
A reminder fires on a timer. A chase has judgement.
Your close software already sends reminders — to email, where the last three died with everything else. Keep the checklist and keep the software. This is only about the asking.