Your brokerage firm prepared Form 990-T and your IRA paid tax on Unrelated Business Taxable Income derived from the MLP. Such income is taxable to the tax-exempt entity that incurs the income, in this case, your IRA. This does not get reported on your personal tax return. Form 990-T is it's own tax return for the entity that is your IRA. Your IRA statement should show a reduction in value by the amount that the IRA had to pay in taxes.
As with any other investment, gains and losses from trading of the MLP within your IRA are not current gains or losses reportable on your personal tax return. You recognize ordinary income when you receive a distribution from your IRA.
