RSU vesting can trigger payroll tax years before income tax

The record

Two separate Internal Revenue Code provisions govern the timing of tax on a restricted stock unit, and they do not always point to the same date. Section 3121(v)(2) sets a 'special timing rule' for Social Security and Medicare tax, FICA: an amount deferred under a nonqualified deferred compensation plan is taken into account as wages for FICA purposes as of the later of when the services creating the right to it were performed or when the right is no longer subject to a substantial risk of forfeiture, in practice, the RSU's vesting date, whether or not shares have been delivered. Treasury's regulation at 26 CFR 31.3121(v)(2)-1 restates this as the 'special timing rule' and adds a 'nonduplication rule': once an amount has been taken into account for FICA under this rule, neither it nor its later appreciation is treated as FICA wages again.

What the documents establish

Section 409A's own distribution-timing rules, at 26 CFR 1.409A-1, govern a different tax: federal income tax on the deferred compensation itself, which can be delayed past vesting if the RSU is structured to settle on a later permitted event, such as a separation from service or a fixed date, rather than immediately at vesting. Read together, the statute and regulations establish that an RSU can vest, triggering FICA under the special timing rule, in a year before it settles and produces the income-tax event under Section 409A's rules, if the award's own terms defer settlement past vesting. Neither provision states that a single settlement structure is required; the regulations describe a timing framework that a plan's own drafting choices operate within, not a single mandated design.

The operating read

Editorially, the practical consequence for an employer is a withholding obligation that can arise at vesting even when no shares have yet been delivered and no income-tax withholding event has occurred, because FICA's special timing rule runs on its own clock. A company that settles RSUs immediately at vesting avoids the gap by design, since the FICA and income-tax events coincide; a company that permits deferred settlement, common in some later-stage private-company plans to manage share issuance timing, takes on the administrative burden of withholding and depositing FICA tax from other compensation in a year when the employee receives no shares from the award being taxed.

What to check before you decide

Before assuming an RSU plan's settlement timing is straightforward, check the following against the plan document.

• Does the plan settle RSUs immediately at vesting, or does it permit deferral of settlement to a later permitted event under Section 409A?
• If settlement is deferred past vesting, has the company identified the FICA withholding obligation that arises at vesting under the special timing rule?
• Does the plan's nonduplication treatment match the regulation's rule that an amount taken into account for FICA is not taxed again as wages later?

This is not tax advice; the interaction between these two timing rules depends on a specific plan's settlement terms, which a payroll tax specialist should confirm.