Does it need a special treatment for selling DVMT due to Dell relisting?

[flattax2]

Due to Dell returning to a public traded company, I got most cash and some DELL shares from my DVMT shares. All my DVMT shares were from EMC ESPP after Dell/EMC merger. Now UBS which manages our stock accounts issued me a 1099-B that showing a huge long term gains. Do I need to adjust the cost basis or just take whatever the 1099-B states?

[TomYoung]

Your obligation as a taxpayer is to report your basis properly such that the gain or loss is correctly reported. 

EMC to DVMT to Dell was a series of complex transactions - accounted for as "sales" - that took quite a bit of effort on shareholders' part to report properly.  Throw in the additional complexity of acquiring your original stock via an ESPP, the sale of which can create "compensation" (which adjusts your basis) and if you've got that all straight then I tip my hat to you.

If you know that the basis reported by the broker is wrong, and can defend that position, then you certainly can change it.

Tom Young