Tax Question??

Okay so I didn't pay my taxes last year, and the IRS has asked me to fill out a form explaining why. There is more than one reason, including not having the money, I was in the middle of moving (and to be honest kinda forgot), at the time I didn't know about filing extensions etcetera, so I figured I would just file both this year. I know the quickest way to get into trouble with this, is to give the wrong response, or give too much information. What should I say?