Calculating max 401K contribution across W2 employer and Solo 401k

[dlj56]

I am trying to determine the maximum employer contribution that I can make to my solo 401k plan, and am hoping someone can help me identify where to calculate this in TurboTax. From my W2 employer, I already contributed $7,186 to my pre-tax 401K for the company match. Given that the 2023 elective deferral limit is $22,500, I also contributed $15,125 to my solo 401k in elective deferrals. I know this is slightly less than the limit, but I thought better safe than sorry. My business made $26,767 net profit after the self-employment tax deduction and I am trying to calculate how much employer contribution I can make to my solo 401k. When I click "maximize my contribution" in Turbotax, it recommends a max contribution of $24,454 which does not seem to include the 401K contribution that I already made with my W2 employer. Can anyone advise on what my solo 401k employer contribution should be?

[paulhart]

Turbo appears to be incapable of handing this situation correctly. The total employee contribution to all 401k's together is limited to the maximum, but the employer contribution of each 401k separately is limited to the maximum. But you will have to calculate it yourself and manually edit the forms. The dialog will not do it correctly, it will pass TT review, but then the IRA will fine you 10% for the over contribution, and TT will say oh yeah it says that in the fine print (it does).  

[dmertz]

As you found, you can't use the Maximize function for a 401(k) contribution.  TurboTax will calculated the appropriate employer contribution if you mark the Maximize box for a SEP IRA contribution.  The calculation method for the employer contribution is the same, and the SEP IRA contribution is only an employer contribution.

[paulhart]

Even if marking the wrong box (the SEP IRA when you really have an SE 401k) did get you the same employer contribution, you still to the maximum employee calculation manually based on your contribution to your employer 401k, then go back to the beginning and manually input all three numbers (six on a joint return) and uncheck all the maximize boxes in all the sections, “individual” (SE) 401k AND “Keogh” (which is incorrectly called “additional” when it is the same one), without skipping it as inapplicable, to force it to accept the correct entries. Otherwise it will tell you to contribute too much and file a return with an illegally excessive refund. 

[dmertz]

You can enter the employee contributions, then mark the Maximize box for a SEP IRA contribution and leave it marked.  It might be safer to do so than to unmark that box and enter the employer contribution manually, just in case some subsequent entry changes the net profit from self employment.