The “Mega Back Door” Roth IRA Contribution
Roth IRAs are
subject to relatively low contribution limits, based on the income of the taxpayer. Rollovers from a 401(k) plan into a Roth IRA are a different story – they have no dollar or income restrictions. As such, these rollovers are often called a “back door” Roth IRA contribution.
Given the very high contribution limits attributable to voluntary contributions, their rollover has been coined a “mega back door” Roth IRA contribution.
Nondiscrimination Testing Can Severely Limit Voluntary 401(k) Contributions
Voluntary contributions are rarely viable in 401(k) plans that benefit both
Highly Compensated Employees (HCEs) and non-Highly Compensated Employees (non-HCEs) due to their impact on the Average Contribution Percentage (ACP) test.
The ACP test compares the average contribution rate for plan HCEs to the non-HCE average. This test fails when the HCE average exceeds the non-HCE average
by more than the legal limit. In a traditional (non-safe harbor) 401(k) plan, both employer matching and voluntary contributions are tested. In a safe harbor 401(k) plan, just voluntary contributions are (usually) tested.
Regardless of whether your plan meets the safe harbor provision or not, voluntary contributions are almost always included in nondiscrimination testing. Essentially, voluntary contributions negate the “free pass” you would otherwise receive in the ACP test, meaning your HCEs would very likely be significantly limited in their ability to do “mega back door” Roth IRA contributions.
Additionally, safe harbor 401(k) plans lose their top heavy test “free pass” when voluntary contributions are made. That could make additional top heavy minimum contributions to “non-key” employees necessary.
As such, voluntary contributions are rarely worth the trouble when a 401(k) plan covers non-HCEs due to their impact to annual IRS nondiscrimination testing.