Are Roth 401(k) Contributions Made Net of Tax?

[Alf]

If an employee with a $1,000 check elects 10% Roth 401(k), is the Roth contribution to the plan $100 or $100 minus the federal income taxes?

[Belgarath]

$100.00. I'm assuming that the entire $1,000.00 is compensation that fits the plan definition of compensation.

[QDROphile]

Whether it is a Roth contribution or an elective deferral, the plan should have some documentation of what it applies a percentage election against, and it needs to communicate that to participants so they can make the intended election. The plan document will usually define compensation rather broadly, but most plans do not apply the percentage aginst all sources. For example, there are elements of W-2 pay that are often missed when it comes to reduciing pay, such as auto allowances. At the end of the day, the deferral amount won't be the same percentage of W-2 pay. Employees usually think of regular gross pay when they make elections.