I use a letter tray called "pending" (aka action support) to hold things like that insurance document until the question is answered.
It is important that nothing gets into the pending tray unless there is already an action related to it in my trusted system. That is, the pending tray is not a dumping ground for unprocessed items.
For projects with long-term or many pages of material, I create a separate folder per project or sub-project. For my largest projects, I have multiple folders and binders. For example, I have an active project with a 3" ring binder, a 1" ring binder, three stick-files of engineering drawings, and twelve manilla folders.