What this line means
The sum of lines 5a and 5b — your total wages and tips that were already subject to Social Security tax through employment. This total is compared against the Social Security wage base on line 7 to determine how much room remains for SE earnings to be taxed at the 12.4% Social Security rate. If you had no W-2 employment during the year, this line is zero.
Does this apply to you?
- You had both W-2 wages and self-employment income during the tax year
- You need to calculate how much of the Social Security wage base your employment wages consumed
- You had unreported tips from Form 4137 in addition to regular W-2 wages
Easy to overlook
High-wage employees who also have SE income often overpay If your W-2 wages already exceed the Social Security wage base ($176,100 for 2025), your SE earnings owe zero Social Security tax — only the 2.9% Medicare portion applies. Line 6 tells you exactly where you stand. Without completing this line, you end up calculating Social Security tax on SE earnings that are already above the ceiling, resulting in overpayment. 1 IRS Schedule SE instructions — Line 6
This line only covers Social Security wages, not Medicare wages Line 6 is exclusively for the Social Security portion of FICA. Medicare has no wage base limit, so Medicare wages from your W-2 are irrelevant here. The Medicare tax on SE earnings (line 10) applies to all SE income regardless of how much Medicare tax your employer already withheld. Do not confuse W-2 Box 5 (Medicare wages) with Box 3 (Social Security wages). 2 General filing pattern — Social Security ceiling miscalculated with multiple income sources
Watch out for this
Leaving this line blank when you had W-2 employment. If you earned any wages subject to Social Security tax, those wages consume part of the $176,100 ceiling. Skipping line 6 treats your entire SE earnings as subject to Social Security tax, potentially charging the 12.4% rate on income that should have been above the cap.
Footnotes
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IRS Schedule SE (Form 1040) Instructions, Line 6. https://www.irs.gov/instructions/i1040sse ↩
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IRS Schedule SE (Form 1040) Instructions, Social Security Wage Base. https://www.irs.gov/instructions/i1040sse ↩