It is most likely caused by the self-employment tax, check Schedule 4, line 57. If you are self-employed you still have to pay the self-employment tax even if that income is excluded.
You can preview your 1040:
- On the left side of your screen, select Tax Tools, then Tools.
- Under Tool Center, select View Tax Summary.
- On the left side of your screen, select Preview my 1040.
