We’ve been using cardboard banker’s boxes for a long time now but for a more permanent solution these well-built plastic file boxes are highly recommended.
We had a large filing cabinet et back in the day when everything was kept on paper. Not necessary any more but there are a few documents we still keep. This was just the right size for downsizing but still keeping important documents in one place. It's light the lid fits great and the files glide nicely. Highly recommend.