My mother passed away in 2011 in Missouri. I received money that she had invested in a Pioneer Fund which stated my name Conduit TOD/MA "Subject to STA TOD Rules" I was told I would not owe taxes when I received this money BUT the IRS says otherwise. I received a 1099-B apparently which was reported and now I got a notice for past taxes. Do I owe taxes on this money?

The IRS thinks you owe the money because you got a Form 1099-B. You need to contact a local tax professional to review the paperwork to see if you can file a return that shows the income as being tax-exempt.

I doubt it, but I cannot be sure without reviewing the paperwork.