"I was under the impression that a solo 401k functioned like a regular 401k."
Nope. Not quite.
On my husband's W2 the amount he contributed to his 401k is not included in his gross income.
And it should not be included in box 1 of the W-2 either. It's in box 12 and most likely the "retirement plan" box is checked on his W-2 also.
When I add contributions to my solo 401k, however, it seems as if my income is unaffected as is the earned income tax credit.
It is affected, with the same end-result. For your husband, his gross income is reduced "before" it's taxed. This is reflected by his contributions not being included in box 1 of his W-2.
For you with a 1099-MISC (indicating you're self-employed) your gross income remains the same, but your *TAXABLE* income is reduced by your contributions. Assuming you file SCH C to report your self-employment income, take a look at line 28 of the Schedule 1. That's included in the total on line 36 of the SCH 1 which gets transferred to line 7 of the 1040.
I thought that if I contributed the entire amount on my 1099-misc to a solo 401k then my income should go to 0.
The maximum amount you can contribute to your solo 401(k) in 2018 is $55,000 if you are under the age of 50. But you can't contribute more than your taxable business income as figured before making the contribution.
