It is entirely possible that you have triggered the Alternative Minimum Tax. TurboTax does not limit them per se, but if the amount is large, the IRS has imposed a tax that is in addition to Federal Income Tax. Look on Line 45 to see if there is an amount there.
Alternative Minimum Tax is calculated
on Form 6251. (https://www.irs.gov/pub/irs-pdf/f6251.pdf). The AMT is a separate tax
that is imposed in addition to your regular tax. It applies to taxpayers who
have certain types of income that receive favorable treatment, or who qualify
for certain deductions, under the tax law. These tax benefits can significantly
reduce the regular tax of some taxpayers with higher economic incomes. The AMT
sets a limit on the amount these benefits can be used to reduce total tax.
Some of the typical items that
trigger it are employee business expenses and these found at the following
link.
http://www.schwab.com/insights/taxes/amt-triggers
