MSNBC reported that they contacted the White House and that the 2005 Form 1040 was confirmed to be Trump's and genuine.

Trump paid taxes and that's no big deal. The real story is still hidden. The 1040 is the only portion that was sent to reporter David Cay Johnston. As he pointed out, the real story is in the details of the supporting forms and documents that haven't been released.

And why would that be of interest? One example has been in the news recently. The Trump organization built a hotel in Azerbaijan, a deal done with the notoriously corrupt Mammadov family with financial ties to the Iranian Revolutionary Guard, a terrorism sponsor and drug trafficker. Additional tax documents might show that Trump violated the 1977 Foreign Corrupt Practices Act. If so, that is an offense that results in jail time.

http://www.salon.com/2017/03/06/trumps-hotel-and-tower-in-azerbaijan-is-ties-to-an-iranian-terrorist-group/

Trump needs to release his tax returns. What is he hiding?