Step 1 of 6 · Who owes the tax
Form 5330 — Section C: Excess contributions to a 401(k) or similar plan
The 10% tax on excess contributions or excess aggregate contributions to a cash-or-deferred arrangement that were not distributed in time.
This return reports Section C taxes only.
A Form 5330 may report the taxes of one section. If you also owe an excise tax from another section, it has its own due date and needs its own Form 5330 — start a second one from the section list.
Due: The last day of the 15th month after the close of the plan year the excess contributions relate to.
Who owes the tax
Form 5330 is filed by whoever is liable for the excise tax. That is not automatically the plan, its sponsor, the account's custodian, the plan administrator, or the person filling this in — and whoever signs is asked for separately, later.