Fool.com seems to think so, but they're not, of course, the authoritative rule on taxation.
"If you are an employee and you have both a 401(k) and SEP IRA through your employer, your deferral contribution to the 401(k) cannot exceed $18,000 ($24,000 if over 50), and the total contributions to both accounts cannot exceed $53,000 ($59,000 including 401(k) catch-up contributions)."
http://www.fool.com/knowledge-center/2016/01/16/can-a-person-have-a-401k-and-sep-ira-simultaneousl.aspxAlso:
"Yes. You can make contributions to both a SEP and a Solo 401K Plan. In other words, a business can have both a SEP IRA and a Solo 401(K) Plan, although, there is generally no advantage for a business to have both active at the same time.
A Solo 401(k) Plan includes both an employee and profit sharing contribution option, whereas, a SEP IRA is purely a profit sharing plan.
Under the 2016 Solo 401(k) contribution rules, a plan participant under the age of 50 can make a maximum employee deferral contribution in the amount of $18,000. That amount can be made in pre-tax or after-tax (Roth). On the profit sharing side, the business can make a 25% (20% in the case of a sole proprietorship or single member LLC) profit sharing contribution up to a combined maximum, including the employee deferral, of $53,000."
http://www.irafinancialgroup.com/can-i-make-contributions-to-both-a-sep-and-a-solo-401k-plan.php--
The second link explains why it's not usually done, but if you're a S-Corp, or Corporation, it's not 25% of profit, but 25% of the employees salary. So for a $50,000/year salaried employee, the total contributions could, in theory, be:
401k employer contribution (25% of salary): 12,500
401k employee deferral: 18,000
SEP IRA contribution (25% of salary): 12,500
Total contributions: 43,000
So the total is still under the 53k limit, and seems like the ideal way to maximize contributions (if permitted), because the S-Corp can't max out to the 53k like a SEP in a LLC can, and the 401k would be limited to $30,500.
Is this something a Tax Attorney would be needed to investigate? I can't find any IRS rules saying why it wouldn't be allowed.
(e.g. if MMM structured the blog as under an S-Corp, and paid himself a salary, instead of just passing through as LLC/Self-employed income, would this be allowed? If so it seems the best way to maximize contributions).
