Sch C line 19

[stepnej]

Do I use this line to report Solo 401(k) matching contributions?

Thank you.

[Critter-3]

NO ... you are NOT an employee on your own Sch C so it is not treated as a deductible employee contribution...  from the Sch C instructions : 

Line 19
Enter your deduction for the contributions you made for the benefit of your employees to a pension, profit-sharing, or annuity plan (including SEP, SIMPLE, and SARSEP plans described inPub. 560). If the plan included you as a  self-employed person, enter the contributions made as an employer on your behalf on Schedule 1 (Form 1040), line 16, not on Schedule C.

[Critter-3]

To enter your self-employed retirement contributions in TurboTax, log into your tax return  (for TurboTax Online sign-in, click Here) and type "self-employed retirement" in the search bar then select "jump to self-employed retirement". TurboTax will guide you on entering this information.     

OR use the tax topics tool ... under the tax tools >> tools >> tax topics 

[stepnej]

Not trying to argue, but:

From Pub 560 Part 1 (last para b4 Part 2) https://www.irs.gov/pub/irs-pdf/p560.pdf :

Sole proprietor. A sole proprietor is an individual who owns an unincorporated business
by himself or herself, including a single-member limited liability company that is treated as a dis-
regarded entity for tax purposes. For retirement plans, a sole proprietor is treated as both an
employer and an employee.

When an employer makes a matching contribution to 401(k) there are no additional FICA taxes taken from the employee. If I make a matching contribution to a Solo 401(k), it follows that that the contribution should be deducted from the SE tax calculation.

Just trying to figure out how to make that happen.

[dmertz]

Although a sole-proprietor is both employee and employer, none of the contributions to your solo 401(k) go on schedule C.  Schedule C line 19 is only for reporting the contributions made on behalf of non-owner employees.  Contributions to the sole-proprietor's own solo 401(k) account appears on Schedule 1 line 16 as self-employed retirement contributions.  In TurboTax this is done through entries on the Keogh, SEP and SIMPLE Contribution Worksheet.