Caveat: always consult your accountant, tax preparer or lawyer if you’re in doubt. This is one area where it’s actually better to keep something than toss it if you’re unsure.
Here’s a simple one from an accounting website. Here’s one from North Dakota State University that has good tips on why to keep records and how to do it. Extension.org offers a fairly long one complete with the reason to keep each document.
Quick Tip: Whenever you open a folder to file something, take a moment to glance through it and see if there’s anything you can get rid of. If you’re filing in reverse chronological order (newest items in the front; I recommend this method), look in the back of the folder first for potential shredder fodder.
Repurposed file cabinet courtesy of ARTS’ photostream.