Pointing out the towering stacks of manila folders cluttering his desk and stepping carefully around the millions of forms laid out on his office floor, Commissioner of the Internal Revenue Service John Koskinen showed reporters Thursday his own personal filing system for keeping track of everyone in the nations tax returns. Im sure anyone who looks at the 100 million folders spread all over my office wouldnt be able to make heads or tails of my method, but trust me, I know exactly where everything is, said the IRS chief, smoothing a yellow sticky note bearing the words Alternative Minimum onto a thick sheaf of documents before stowing it away in one of his 750,000 accordion folders. All the files piled on my couch are 1040s, but the red folders are for married and filing jointly and the blue ones are for single with at least three dependents. I know it sounds confusing, but it makes sense to me. Please just dont touch anything; I had to start all over last week when someone from maintenance came through and moved some 1099s around. At press time, Koskinen went to retrieve a box of 122 million W2 forms from the back room to double-check a figure from last year. 