I am trying to calculate the profit sharing maximum for my solo 401k. I have already used my employer 401k maximum at $18k.

[giova]

If I check "optimize" box in the Business Individual 401k section, it assumes I did not put money in my company 401k...

[Critter]

If you have maxed out the employer 401K then you may not make any further 401K contributions at all.

[SweetieJean]

<a rel="nofollow" target="_blank" href="https://www.irs.gov/retirement-plans/one-participant-401k-plans">https://www.irs.gov/retirement-plan...>

[giova]

that's incorrect - you can make employer profit sharing contribution...

[SweetieJean]

I suspect that part of the program isn't finalized yet.

[Critter]

<a rel="nofollow" target="_blank" href="https://www.irs.gov/retirement-plans/choosing-a-retirement-plan-profit-sharing-plan">https://www.irs...>

<a rel="nofollow" target="_blank" href="https://www.irs.gov/retirement-plans/self-employed-individuals-calculating-your-own-retirement-plan-...>

<a rel="nofollow" target="_blank" href="https://www.irs.gov/retirement-plans/plan-participant-employee/retirement-topics-401k-and-profit-sha...>

[dmertz · Accepted solution]

TurboTax does not support automatic calculation of your maximum deductible contribution to a solo 401(k) when you have made elective deferrals or Roth contributions to another employer's qualified retirement plan.  This is explicitly documented as unsupported:  https://ttlc.intuit.com/questions/1901702-are-there-any-personal-individual-tax-situations-or-calcul...

Since you have already made the maximum permissible elective deferral and therefore cannot make any elective deferral or Roth contribution under your solo 401(k) plan, you can instead mark the Maximize box for a Keogh profit-sharing plan.  This will cause TurboTax to calcutate only the maximum employer contribution permissible to your solo 401(k).  Indicate No, you did not contribute to an Individual or Roth 401(k) plan, then indicate Yes, you contributed to a Keogh plan, then mark the Maximize box for the Profit Sharing Keogh Plan.  The calculation of the employer contribution is the same as for a 401(k).

[dmertz]

Also, first go through and indicate that you *did* make an Individual or Roth 401(k) contribution, then on the next page make sure that all of the boxes, including the Maximize box, are blank.  Having Maximize boxes marked on more than one of the pages will get the wrong result.

[Zbucklyo]

The maximum employer contribution is approximately 18.57% of your net profit from self-employment.  The total of your entire solo 401 (k) contribution, one half your self-employment tax, and deduction for self-employed health insurance premiums can't exceed your net profit from self-employment.