This is a remarkably accurate comment on this topic. Few docs and similar professionals have this level of financial literacy.Before anyone gives you advice, you need to ask them what the difference in the 402g and 415c limits are...if they can't immediately be more helpful than a google search for this question, they don't know enough to help you and are likely to say things that aren't true. You basically get one employee 402g limit across all accounts but an independent 415c limit for each account.
You can mega backdoor at both if you have a solo 401k that allows it:
https://www.whitecoatinvestor.com/retir ... unts/#self
For the amounts you are talking about, and given year to year variation, might be easiest to just contribute after tax (then automatically convert, ie mega back door) in the solo 401k up to the 415c limit rather than figuring out each maximum contribution. Be mindful that if your side income is not significantly higher than the 415c limit you need to be aware that the maximum contribution may be less than what you made after payroll calculations.
BTW, the first thing anyone needs to know about solo 401k is the 5500-EZ form before you learn the hard way in a few years. Doing all after tax/mega backdoor and using a provider that allows transfer to roth IRA can skip this though (at possible expense of asset protection based on state).
Statistics: Posted by White Coat Investor — Tue Jan 27, 2026 12:07 pm — Replies 4 — Views 320