After-tax contribution

After-tax contribution. An after-tax contribution is money you put into your 401(k) or other employer sponsored retirement savings plan either instead of or in addition to your pretax contribution.

You make an after-tax contribution if you've chosen to participate in a Roth 401(k) or similar tax-free plan rather than a traditional tax-deferred 401(k).

However, if you make excess deferrals, any earnings on the after-tax amount accumulate tax deferred. The disadvantage is that figuring the tax that's due on your required distributions may be more complicated than if you had made only pretax contributions.