401k pretax limit is 18,500. Some plans allow additional after tax money after reaching the pretax limit. Does the after tax portion reduces ones AGI?

[dmertz · Accepted solution]

No, an after-tax contribution does not reduce your AGI.  Being included in your AGI is what makes it an after-tax contribution.

When you eventually make distributions from the plan, the portion of each distribution that is after-tax basis does not add to your AGI for the year of the distribution.