What this line means
The combined total of lines 4a and 4b. This is your total self-employment earnings subject to SE tax. If this amount is less than $400, stop here — you do not owe self-employment tax and do not need to complete the rest of Schedule SE. The $400 threshold is the gateway: below it, no SE tax; at or above it, the full amount is taxed.
Does this apply to you?
Easy to overlook
The $400 threshold applies after the 92.35% adjustment, not before The $400 test uses line 4c, which is based on 92.35% of your net earnings (or optional method amounts). A sole proprietor with $430 of net profit on line 3 has $397 on line 4a after the 92.35% multiplier — below $400, so no SE tax is owed. The threshold is tested against the adjusted amount, not the raw net profit. 1 IRS Schedule SE instructions — Line 4c
Falling below $400 means zero Social Security credits for the year If line 4c is under $400 and you did not use optional methods, you earn no Social Security credits for the year. Self-employed individuals need to earn at least $400 in net SE earnings (after the 92.35% adjustment) to receive any credits. For someone close to qualifying for Social Security benefits, losing a year of credits has long-term consequences. The optional methods in Section B exist specifically for this situation. 2 General filing pattern — SE tax filed when earnings below $400
Watch out for this
Completing the rest of Schedule SE when line 4c is below $400. If line 4c is less than $400, you do not owe SE tax. Continuing to calculate lines 5 through 12 produces a tax amount that you do not owe, and entering it on Schedule 2 overpays your tax bill. Stop at line 4c if the amount is under $400.
Footnotes
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IRS Schedule SE (Form 1040) Instructions, Line 4c. https://www.irs.gov/instructions/i1040sse ↩
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IRS Schedule SE (Form 1040) Instructions, When To File Schedule SE. https://www.irs.gov/instructions/i1040sse ↩