I've never understood how sub-categories work with filing folders, at least with the ones I've used the labels get hidden and the inner folder looks messy. That and I can never stick with the same categories. In theory, I wish I could use a filing cabinet as you described bandicoot. Car insurance (the card or a new policy?) would be in the folder for current policies, an easy swap.
Something I thought of but didn't use, is a folder with folders inside (something like this https://store.schoolspecialty.com/OA_HTML/ibeCCtpItmDspRte.jsp?minisite=10224&item=491066). Would allow for categories or narrowing the chronological files.
