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Unfortunately, TT doesn't support form 8990.  You can download it from the IRS website, fill it out, and then add it to your return (which you'd have to print and file by mail).

If all you have is 20AE "Excess Taxable Income", you shouldn't need to file it.  But when you get an entry for "Excess Business Interest Expense" (box 13, code K), you'll need to.  Here's the "Who Must File" section from the form:

A taxpayer with business interest
expense; a disallowed business interest
expense carryforward; or current year or
prior year excess business interest
expense generally must file Form 8990,
unless an exclusion from filing applies.
     A pass-through entity allocating excess
taxable income or excess business
interest income to its owners (that is, a
pass-through entity that is not a small
business taxpayer) must file Form 8990,
regardless of whether it has any interest
expense.
     A taxpayer who is a U.S. shareholder of
an applicable controlled foreign
corporation (CFC) and such CFC has
business interest expense, a disallowed
business interest expense carryforward; or
is part of a CFC group election must
generally apply section 163(j) to each
CFC and attach a Form 8990 with each
Form 5471. See Proposed Regulations
section 1.163(j)-7(b).