Low Income Roth 401(k) and Roth IRA Combination

[RTN1]

My son is 20 and makes W2 income $8000/year.

He can contribute up to 80% of his income into a company Roth 401, and get matching non Roth contribution.

Can he also contribute the full $6500 into a Roth IRA, or is this reduced based upon low total income?

Is $8000 the max for all Roth accounts combined, or can he double up across different Roth accounts?

[Opus 17]

I want to recruit an expert to this conversation.

@dmertz 

I reviewed publication 590-A and I did not see a requirement that his eligibility (compensation) was reduced by the amount that was contributed to the Roth 401k.  I think, like you probably think, that it would be logical that his eligiblity would be reduced, but I don't see that in writing.  (And it would be reduced by a pre-tax 401k since that reduces his W-2 box 1 wages.  But I don't see it for a Roth 401k.)  But I want to double check with another expert who knows all the details of these plans.

[dmertz]

Opus 17 is correct.  The amount in box 1 of your son's W-2 is compensation that will support an IRA contribution, traditional or Roth, regardless of how much of his compensation is contributed to the Roth 401(k).