One of the first things I would do is compare your return line by line to last year's return. Maybe you will spot something that was entered different or on the wrong line, etc. Or you left something out. Maybe your filing status is wrong. Did you file as Single? Are you divorced? When?
Turbo Tax is a self prepared return. They only guarantee the calculations are right based on your entries. They won't know if you entered something wrong or twice or in the wrong place or left something out. It doesn't check against any outside sources. The IRS has copies of all the W2s and 1099s your employer and banks/brokers, etc. sent in to match against. Turbo Tax only checks the calculations of what you entered. It is your responsibility to check it over before you file.
