Today I spoke to my accountant about my 2019 solo 401k contributions. He was entirely unfamiliar with the mega backdoor Roth concept. Once I explained it to him, he got it, sort of. Then he asked me a question that stumped me: he wanted to know if my business was going to be making a separate business contribution to a SEP IRA account on a tax deferred basis and whether I was going to take a deduction for it.
That got me thinking. Since I made a 25k personal contribution to my Roth solo 401k and a 37K contribution to a voluntary after tax account, my business in effect contributed nothing to my retirement plans. Were I to set up a SEP IRA, would it be possible to do another 37k contribution to that new account on a tax deferred basis? Or is there some overall limit I might hit?
You have already maxed out your 2019 contributions. The overall limit for 2019 is $56,000 therefore you cannot make a tax deferred contribution to a SEP-IRA because you would then over contribute.
A SEP-IRA is considered a Self-Employed plan just like a Solo 401k so the contributions would be aggregated across the two accounts/plans.