Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of Iron Mountain (NYSE:IRM) dropped 16% today after the company revealed that the IRS is looking into its switch to a REIT structure.

So what: An SEC filing revealed that the IRS is looking into "multiple components" of the company's REIT request and must rule favorably on all of them. You can click here for the full filing but it doesn't look like the IRS is inclined to allow Iron Mountain to become a REIT in its current form.  

Now what: Companies try to convert to REITs to save on taxes -- and companies are now trying stretch that definition as far as they can. Iron Mountain doesn't look like a REIT on the surface, and I would be surprised to see a positive ruling from the IRS. This definitely isn't a reason to buy today, and I'd watch this investigation closely going forward.

Interested in more info on Iron Mountain? Add it to your watchlist by clicking here.

Fool contributor Travis Hoium has no position in any stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.