Don’t start a To Be Filed pile.
I mean, you can make such a pile temporarily, when you’re opening the mail and paying bills and such, and then get up and file everything in that pile as soon as you’re done–that’s a fine strategy. What you must avoid is making a pile of things you are going to file away in their proper places Someday when you Have Time. That day may not come until the pile is very big, and then it will look so daunting that you will do everything in your power to avoid Having Time to sort and file all those boring papers. Meanwhile, the pile will take up space and serve as a constant reminder of how busy you are now and how stupid you were then.
I started a To Be Filed pile when I was pregnant and exhausted. My child is now six years old, and I still have not cleared out that pile! I succeeded in stopping myself from adding to the pile quite some time ago, and several times I have worked on it for a while and filed some of it (much of it can now be filed in the recycling bin, since it is outdated), but I have never yet reached the bottom.
Don’t do this. File those papers now, or just recycle them. Your future self will thank you.