I echo what previous poster has said....why drowning in paper? There is very little that you need to keep on paper except the essentials. I do all my banking online for instance, and do not have paper statements for credit cards, bank or savings accounts as these can all be looked at online. I have standing orders going into them/out of them for payments which makes life easier; all my bills are also paid by standing order/direct debit so I know what is going out or coming in and I don't need to monitor it except check online regularly.
For filing the important things, I have 5 files - these are just plastic wallets. One is for the car...tax, MOT, insurance, car payment agreement, that type of thing. The 2nd is for personal documents - here I save old GCSE certificates, job contract papers, training certificates. When the children were at home their things were in here too - birth certificates, my marriage cert....but it's emptier now everyone has left home!
I guess you would keep your passports in this folder too but I actually carry my passport round with me in my handbag as I often need it for ID.
A 3rd folder is for finances - tax codes, payslips, any credit agreements and so forth. Each month I throw in my payslip but every year I go through the file and 'cleanse' it of old papers...I never keep payslips more than a year, there's no point. Really no need to have 6 year's worth...although I've been in my job for several years now....I guess if you were chnging jobs a lot you would want to keep the records for longer in case there were tax implications that needed sorting out.
In this folder you would also want mortgage papers or renting agreements....
A 4th folder is for medical stuff...as I'm older I have a medical condition which requires some test results etc. Here are NHS cards, the old notes from when I had my babies (sentimental value!!) and medical notes from the chidlren etc. If you had a family still at home all the family's medical stuff would be in here too.
The final folder has guarantees and applicance notes. I know it sounds odd, but each time I buy something I keep the little booklet of instructions (especially electrical goods) so that i know where to find it if anything goes wrong. Here I also keep waranties, furniture guarantees or washing machine instructions. However, I don't keep receipts for everything I've bought - no need - just big items.
These days the folders aren't very large but they were much bigger when I had a whole family to track. We never had any pets but I guess if you had animals - cats/dogs, horses, you would want another folder for them to track costs and vet's bills or innoculations...
But it shouldn't be very complicated, such files take an A4 space in the corner of one cupboard.....