How would IRS contact a person?

If a CD was cashed in (early withdrawal and penalty paid), would a person owe taxes on the money withdrawn? I don't believe this money would be taxable, since it came from the sale of my home, but my ex said I was reported to the IRS, and may just be bluffing me. It's been four years and it has been brought up to me several times as being reported. If indeed it was reported to IRS, how would they contact me? Would they send a certified letter, or would they come pounding on my door with handcuffs? Does anyone know first hand how you would be contacted? This is really making me crazy with worry. Like I said, my ex probably is just trying to get my goat and make me worry about something that won't even happen, but keeps telling me that half of the money belonged to them because it was taken out in both names. In fact, I don't even think the money was taxable, since I lost because of early withdrawal.