Guide · Equity compensation
Sell-to-cover, explained (and why it still leaves you short)
Sell-to-cover feels like the tax is handled: shares vest, some are sold, withholding is remitted. What it actually covers is the flat 22% — and if your bracket is higher, the rest is due in April.
The short answer
Sell-to-cover is your broker paying the withholding, not the tax. When shares vest, the broker sells just enough of them to remit the flat 22% federal withholding and hands you the rest. That 22% is a placeholder: the vest stacks on top of your salary at your real marginal bracket, and every dollar taxed above 22% stays due in April. On a $60,000 vest at a $120,000 salary, the handled part is $13,200 and the part that is still on you is $1,164.
Size your own gap: RSU withholding-gap calculator →
What sell-to-cover actually does
The mechanics are simple. Shares vest, and their fair-market value becomes wages. Your broker immediately sells enough of those shares to remit the required withholding, and the remaining shares land in your account. One thing to know about the withholding being funded here: it is income tax only. Social Security and Medicare come out of the same paycheck separately, so the pay stub and the share sale are doing different jobs.
The worked example: 1,000 shares at $60
1,000 shares vest at $60: a $60,000 vest, added to a $120,000 salary, single filer. The broker sells 220 shares to fund the 22% withholding — $13,200. You keep the remaining 780 shares. It feels finished. It is not: the true income-tax slice on that vest is $14,364, an effective 23.9%, because the vest stacks from the top of the 22% bracket into the 24% bracket. The $1,164 difference — 1.9% of the vest — is a bill due in April.
Why the gap exists
The 22% is a flat withholding convention, sized to the 22% bracket. Your tax is not flat: the vest stacks on top of your salary, and every vested dollar lands in whatever bracket your income has already reached. At a $120,000 salary the stack starts near the top of the 22% bracket, so the leak is small — cents per dollar. At higher salaries it widens fast. The full salary-by-salary table lives in the companion guide: why the 22% RSU withholding falls short →.
The second taxable event nobody mentions
The 220 sold shares are not taxed twice — but they are taxed again on any movement after vest. Their cost basis is the vest-day price, $60. Sell at $62 and the $2 rise is a $440 short-term capital gain, about $106 of additional tax at a 24% marginal rate. Sell at $58 instead and the $440 loss offsets other gains. (The wash-sale rule rarely bites here — you are selling, not repurchasing.) The wage tax was settled at vest; this is a separate, smaller event, and it is easy to forget it exists.
What to do about it
- Elect a higher withholding rate with your plan administrator, if the plan offers one — many allow 37%. One setting, no calendar.
- W-4 line 4(c) extra withholding: divide the gap by your remaining pay periods — $1,164 ÷ 26 biweekly checks is about $45 per check if you start in January. Withholding counts as paid evenly all year, which makes this the forgiving option.
- Quarterly estimated payments keyed to each vest date. Precise for irregular vests, but credited only to their own quarter.
Run your own numbers with the RSU withholding-gap calculator, and check whether the gap threatens a penalty with the safe-harbor guide. The gap appears the day you vest and moves every quarter after: the live monitor dashboard shows your bracket position in real time (labeled sample; account connections are planned, not live).
FAQ
Does sell-to-cover cover all my tax?
No. It funds the flat 22% withholding, not your bracket. In the worked example above, sell-to-cover remits $13,200 of the $14,364 the vest really costs at a $120,000 salary, leaving $1,164 due in April.
Do I pay tax again on the shares that were sold?
Only on what the price did after vest. The 220 sold shares were already taxed as wages at vest; selling them later is a separate capital gain or loss on the post-vest movement alone. A $2 rise on 220 shares is a $440 gain, about $106 of tax.
Can I choose a different withholding rate?
Plan-dependent. Many administrators let you elect a higher rate — some allow 37%. If yours does not, the same result comes from W-4 line 4(c) extra withholding or quarterly estimates.
A guide answers this once. TaxGhost answers it every month — the monitor recomputes what you owe each time your income changes.
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