Does anyone know how to get the resolve date mismatch task to appear on the close checklist? Is this only for inventory? I am trying to figure out why I've seen this at past company's but do not in my current Netsuite instance.

There is a setting in accounting preferences that allows users to set the accounting period separate from the date. Is that enabled? If not I don’t think there is a need for that task so they don’t show it

Yes, this is enabled.