Does self employment tax affect my fed tax return?

[Vanessa]

Yes, self-employment tax is added to your tax liability and then deducted from your refund or it will cause you to owe money.  

Also, 1/2 of your self-employment tax is deducted from your Income to arrive at your Adjusted Gross Income. 

[VolvoGirl]

Self Employment tax (Scheduled SE) is automatically generated if a person has $400 or more of net profit from self-employment.  You pay 15.3% SE tax on 92.35% of your Net Profit greater than $400.  The 15.3% self employed SE Tax is to pay both the employer part and employee part of Social Security and Medicare.  So you get social security credit for it when you retire.  You do get to take off the 50% ER portion of the SE tax as an adjustment on 1040 Schedule 1 line 27.   The SE tax is already included in your tax due or reduced your refund.  It is on the 1040 Schedule 4 line 57 which goes to 1040 line 14.  The SE tax is in addition to your regular income tax on the net profit.