Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:4847593.

A 2-part box to keep your A4 documents organized for a long term storage. Offer at 3CM and 1CM storage size

1. Put papers in the bottom part.
2. Then put the top part in.
3. Use the cut-out to move the parts in place.
4. Push + slide the top part on the curve to lock the box in place.

I don't know how long your tax bandit requires you to keep your papers, but mine is up to 7 years. There is no good way to do that. So, I design this and print one. Given the rectangular profile, this should allow easy storage and keep all the moisture and bugs out. If you aren't too sure, coat it and tape the middle part shut. Keep it organized and away.