Solo 401k calculation

[SEAMountaineer]

Hi all,

In 2025, I had $19,153.75 of 1099 income. I opened a Solo 401(k) and contributed $17,800, but TurboTax is telling me "Using the maximum allowable contribution, you can defer a maximum of $17,690 to a 401(k) plan." Does anyone know how they are getting this calculation? 

I had calculated using this: =$19,153.75-(($19,153.75*0.9235*0.153)/2)

I checked a few online calculators (including Fidelity, where my Solo 401k is held) and they indicated max contributions of $17,800.

In addition, I had a total of $141k in W2 income, but only contributed $915 to my employer's 401k, so did not reach the max 401k limits for the year.

Is there something I am missing here that would explain the discrepancy in max allowable contributions? I just want to figure out what is going on before I pull $110 in contributions from my Solo401k.

Thank you!

[dmertz]

A maximum contribution of $17,690 implies net profit of $19,035.  Did you enter $119 of expenses that reduced your net profit from $19,154 to $19,035?  Examine your Schedule C net profit shown on Schedule 1 line 3.

[SEAMountaineer]

Ah, problem solved. Yes, I had entered $119 in expenses for a laptop docking station. Once I removed that, the calculation for allowed contributions to my Solo 401(k) increased to $17,801. Thank you so much!