First you really should be talking to a local financial planner to get educated on all these retirement situations ... and where ever you have your solo 401K should also be able to explain your options.
Some follow up questions:
1. I understand I can contribute up to a max of $57K (employee + employer portion) across my Solo (Individual) 401K AND Solo (Individual) Roth 401K. Assuming I can make a contribution of $40K into my 401K(s), can all of it go into the Roth 401K? or is the first $19,500 tax-deferred and have to go into the Solo (Individual) 401K? The employEE portion can go in either account however the employER portion would go to the reg 401K only.
2. To contribute to a Traditional IRA in 2020, your MAGI (modified adjusted gross income) needs to be less than $124,000. To contribute to a Roth IRA in 2020, your MAGI (modified adjusted gross income) needs to be less than $139,000
Are capital gains from investments counted in the MAGI (modified adjusted gross income) thresholds for the Traditional and Roth IRAs? Yes they are if they are taxable on the return.
If not, then my MAGI would be $100K (1099 income) + $60K (part-time W2 income). Assuming I made a contribution of 40K into my solo 401K, would my "tax basis" be reduced to $120K, so that I could contribute to the Traditional / Roth IRA? You can always make a traditional IRA contribution ... it is the deductibility that is in question ... best advice I can give is to NOT make any contributions to any plan until you have your final numbers at the end of the year ... you have until the filing deadline to make them so don't be in a hurry where you are forced to remove excess contributions. See the info below:
Modified Adjusted Gross Income (MAGI)
The IRS uses your modified adjusted gross income (MAGI) when it comes to IRA limits. This number can be close (or identical) to your adjusted gross income (AGI). It takes your AGI and adds back certain deductions, including:
To calculate your modified adjusted gross income, find your AGI from your tax return. It's on line 8b of the newly redesigned Form 1040.9 Then, use Appendix B, Worksheet 1 from IRS Publication 590-A to modify your AGI for IRA purposes.
3. If so, would I qualify for the Mega Backdoor Roth? This is basically a conversion after making regular contributions ... of course a backdoor only really works if you have no basis in your 401K or traditional IRA ... please talk to someone locally for more personalized advice.
