How to report excess after-tax Solo 401K contribution on 1099R?

Taxes Discussions Forum
1

I contribute to my after-tax Solo 401K every year and then roll those funds into my Roth Solo 401K (Mega Backdoor Roth).

I’m unsure how to report these contributions on Form 1099-R and other tax forms.

Since the contributions aren’t deductible, there’s no tax impact, but I want to make sure I report them correctly.

Any guidance?

2

Are you asking about removing an excess contribution or just rolling after-tax funds into Roth?

3

Hayley said:
Are you asking about removing an excess contribution or just rolling after-tax funds into Roth?

For 2024, there was a small excess contribution to the after-tax account. I refunded it to myself before rolling the rest into my Roth Solo 401K.

4

@Palmer
For the excess contribution refund, Box 1 of Form 1099-R should show the total distribution amount. Box 2a should reflect any gains included in that amount, which are taxable. Box 7 would likely need code 8 (excess contribution refund).