I can't be sure, but you may have fallen victim to the Alternative Minimum Tax.
If you are Online, you can view your taxes and Schedules 1, 2, & 3
- On the menu bar on the left that shows.
- Select Tax Tools
- On the drop-down select Tools
- On the popup menu
- Select View Tax Summary
- On the left sidebar
- Select Preview my 1040.
- Schedules 1,2 & 3 are included if you scroll down past your 1040.
- To return to the entry screens press Back on the sidebar.
Please check line 17 on your tax return
This is ladled Amount from Schedule 2, line 3
On Schedule 2, line 3 includes the Alternative Minimum Tax
If you want to follow the documents through the Alternative Minimum Tax is calculated on FORM 6251
For additional information, please see the TurboTax article Alternative Minimum Tax: Common Questions