I do the following:
First, I scan everything. Stuff like statements and bills that come in pdf form, I save. Everything is organised into a folder for each company/account/doctor/whatever, and under that a folder for the year. Then name them by the date issued. For example, I get two types of documents from my bank - statements and advice letters - the latter is stuff like informing me of an interest rate hike or whatever. So I would name them 20230114-Statement.pdf and 20230114-Advice.pdf and if it's a letter arriving in the post (usually something that still has a legal requirement for paper copy), 20230114-Letter_key_word.pdf, where key word is just a word or two to give an indication what it is about.
For paper bills and statements, I scan everything, and add to the folders above. I keep the last 3 months paper for bills and statements. For documents of greater importants - policy certificate, loan, etc, I keep the paper until that item has been completed, whatever that might entail. But I still scan it as above.
Medical stuff I tend to keep paper copies of (still, scanned). I don't mean bills or receipts, but stuff like test results, prescriptions, x-rays, etc. This is more because I've lived all over the world and sometimes want to be able to show something from the past to a new doctor. Not strictly necessary, but sometimes it's just more convenient.
Receipts - scan them all. I thow most away unless it's something where there's a decent chance I might need the warranty. These days almost all purchases that fall in this category start or end with an online order, or at least an electronic receipt, so this is a bit redundant. In this department I have a few slips for computers tuff, a kettle, a coffee machine, but pretty much everything else is either electronic anyways, or thrown out.
Invest in a decent scanner. Something like the Small business/home business targeted laser printer scanner combo, with a document feeder - this makes scanning a lot easier. I say laser printer, because, in my experience the scanners that come with them tend to be mechanically more durable. I have a
Brother DCP-L2540DW that's 9 years old and despite scanning all that time and all my documents for 2 decades before, it's still working like on day one. It can do two-sided printing, has a document feeder and can do two-sided scanning. Brother is still releasing updated drivers after all this time too.
There's another big benefit to laser printers. If, like me, you only occasionally need to print, and tend to print stuff like application forms or proof of this or that where there's a chance some government official is going to drool on it, laser toner don't smudge like ink does. Toner cartriges also don't become unusable after a short time like ink. In my inkjet days, I would print something every 3-6 months, and I'd have to buy new cardtridges every single time. With the laser printer, I'm still on the cartdridge it came with. Also, the toner is much much much cheaper per page.
Lastly, but very important. Make sure you have a proper backup strategy. Something like "3-2-1", i.e.:
At least
Three copies - on a spare hard drive, usb stick, write a CD, whatever.
At least
Two mediums - Don't have three CDs. Your CD writer might be faulty and all three discs useless. You want some diversity here
At least
One off-site copy - oneline backup or leave an external drive at your parents' house. For this one, I used to use two hard drives, one stayed at work in my locked drawer, the other at home, and I swapped them every week or so.
With all this in place, you don't need to keep mountains of paper around, and can be confident you can find an old document at a moment's notice, should you need to. You just have to be disciplined about scanning and filing.
