Meta Staff Engineer: $800k RSU Year and the 37% Withholding Gap
A staff engineer at Meta pulls $800k of annual RSU income and discovers the 22% supplemental withholding leaves a six-figure shortfall. Here is how he covered it.
A staff engineer at Meta, married filing jointly, lives in Palo Alto. His 2025 comp structure: $355k base, $175k target bonus, and $800,000 of RSU vesting spread across four quarterly tranches at the end of February, May, August, and November. His spouse earns $210k as a product manager at a public-market biotech. Combined household W-2 wages for 2025 print at $1.54M. The problem is not that he cannot pay the tax. The problem is that Meta’s default supplemental withholding is going to undercollect by $108,000, and he does not realize it until his CPA runs a March projection and tells him he is already $30,000 behind for Q1.
Situation
Grant stack:
- 4,000 RSUs on a standard 4-year quarterly vest, granted Feb 2023 at $165.
- 2,200 refresh RSUs granted Feb 2024 at $485.
- 1,600 refresh RSUs granted Feb 2025 at $610.
His 2025 vest count across all three grants is approximately 1,310 shares. At an average vest-day price near $610, that is $799,100 of supplemental wages. Add $355k base and $175k bonus and his personal W-2 prints at $1.33M. Combined household wages land at $1.54M.
California tax picture is ugly. At $1.54M of taxable income, they are in the 37% federal bracket (above the $751,600 MFJ threshold for 2025), the 3.8% NIIT zone on investment income, and the 13.3% California top bracket. Total marginal rate on the last RSU vest is approximately 54.1%. Meta’s supplemental withholding is 22% federal plus 10.23% California supplemental. That is 32.2% against a true marginal of 54.1%, a 22-point gap on $800k of RSUs, or $176,000 of under-withholding on the RSU slice alone.
His 2024 tax was $521,000. Safe harbor under IRC §6654 at their AGI requires paying in 110% of prior year, or $573,100 of combined withholding plus estimated payments. His projected 2025 W-2 withholding: $440,000. Gap to safe harbor: $133,100.
What we modeled
| Approach | Mechanism | Effect |
|---|---|---|
| Pay the gap as Q4 estimated | $133k check January 15 | Covers safe harbor but leaves Q1-Q3 underpayment penalty of ~$4,200 |
| Bump W-4 additional withholding | $5,500/pay period x 24 pay periods = $132k | Deemed ratable under §6654(g), no penalty |
| Sell company stock and use proceeds | Liquidate $160k of long-term shares at 23.8% LTCG | Covers tax but triggers $38k of capital gains tax |
| Roth conversion shield | Not applicable, no pre-tax IRA balance | N/A |
Option 2 won on arithmetic. The W-4 bump converts what would be a penalty situation into ratable withholding. Meta’s Workday lets employees set additional withholding directly, so there was no friction. He increased line 4(c) to $5,500 per pay period starting in the April 1 paycheck. Over 19 remaining paychecks that pulled in $104,500. He paired that with a $30k Q2 estimated payment made June 15 to cover the January-through-March shortfall, and a $5k Q4 cleanup payment January 15.
What they did
He set the W-4 at $5,500/pay period, made a $30k Q2 estimated payment, and a $5k Q4 payment. Total extra federal pulled in: $139,500. Federal tax at filing: owed $4,800, inside safe harbor.
On the California side, Meta’s 10.23% supplemental is closer to the actual 9.3%-13.3% marginal but still undercollects. They set Franchise Tax Board estimated payments of $12,000 at each of the Q2, Q3, and Q4 deadlines. California has weird quarterly weighting: 30% in Q1, 40% in Q2, 0% in Q3, 30% in Q4. They missed the Q1 weighting by starting in Q2, which cost them a small penalty (~$480), but the alternative of a single large April 15 payment would have been worse.
Separately, he maxed the Meta Mega Backdoor Roth. Meta’s 401(k) plan allows up to $34,500 of after-tax contributions in 2025 (the gap between the $23,500 employee deferral plus company match, and the $70,000 415(c) limit), with in-plan Roth conversions. That moved $34,500 into Roth where it will grow tax-free forever. The contribution came out of his RSU vest proceeds, not cash flow, which made it feel painless.
What he wishes he had done differently
The Mega Backdoor Roth was new to him as of March. He had been at Meta for 27 months by that point. Missing 2023 and 2024 cost him $69,000 of Roth contributions. At 30 years compounding at 7%, that is $525,000 of tax-free growth left on the table. Meta’s benefits portal mentions it but does not push it, and he had never opened the “401(k) After-Tax” accordion on the Fidelity NetBenefits page.
The second regret is concentration. He was holding roughly $1.9M of vested Meta stock by March 2025, all accumulated from prior vests. Meta stock had a strong run, so it felt fine. But his base, bonus, RSUs, and the bulk of his net worth were all tied to one ticker. A single 30% drawdown in Meta would wipe out $570k of net worth while simultaneously cutting the market value of his unvested equity. We modeled a 10b5-1 plan to sell $40k per month starting in Q3, and in hindsight he wishes he had started it in January.
Third regret: his spouse’s biotech ESPP. She had been accumulating $25k/year at a 15% discount and not looking at it. She had $94k of company stock sitting in E*TRADE, some at a loss. They could have used tax-loss harvesting against the $48k of gains from diversifying Meta. He missed the coordination.
Frequently asked
At what point does the 37% supplemental rate kick in?
Only on cumulative supplemental wages above $1 million in a calendar year from a single employer (Pub 15, Section 7). Below $1M, employers may use the 22% flat rate. If your total RSU income is above $1M at a single employer, everything above $1M is withheld at 37%, which closes the gap.
What is the Mega Backdoor Roth and does my employer offer it?
It is the strategy of making after-tax 401(k) contributions (not Roth, not pre-tax) up to the 415(c) limit ($70,000 in 2025 minus employee deferrals and match), then converting those after-tax dollars to Roth either in-plan or via rollover. Your plan has to allow both after-tax contributions and in-service distributions or conversions. Meta, Amazon, Google, and Microsoft all allow it. Apple and Nvidia do not, as of 2025.
Does the Additional Medicare Tax on RSUs get withheld automatically?
Your employer withholds 0.9% Additional Medicare Tax on wages above $200k from that employer. But if both spouses earn $150k, each employer sees only $150k, no withholding, and you owe 0.9% on the combined excess over $250k at filing. Common trap.
Is there any benefit to holding vested RSUs versus selling immediately?
No tax benefit. The basis is the vest-day price and the cost has already been recognized as ordinary income. Holding is a new investment decision to buy company stock at the current price. The only non-tax reason to hold is trading-window constraints.
How does California treat RSU income that vested after I left California?
California uses a workday sourcing rule. If you vested after moving out, California still taxes the portion of the vest attributable to workdays performed in California between grant and vest. See FTB Publication 1004.
Composite scenario drawn from common patterns in our advisor network's casework. Names, companies, and exact numbers are illustrative. Not tax, legal, or investment advice.