Chapter 4: RSUs end to end
Maya's tax return showed a balance due of $14,030 last April. Nothing was filed wrong. Her W-2 was accurate, her broker reported every sale, and her employer followed the withholding rules to the letter. The bill exists because RSU income is withheld at one rate and taxed at another, and for a high earner the difference quietly compounds all year. This chapter follows an RSU from grant to vest to sale, marks the two moments where tax actually happens, and shows you how to close Maya's gap months before it can become yours.
Grant day: nothing happens
When your company grants you RSUs, you receive a promise of future shares, a vesting schedule, and no tax bill of any kind. Nothing appears on your W-2, nothing is withheld, and there is no election to file. An RSU grant is a schedule of conditional future paydays, which is exactly how chapter 2 taught you to read it.
This makes RSUs the rare instrument with no decisions at the start. You cannot exercise them, you cannot file an 83(b) election on them (that form belongs to restricted stock, a different instrument), and you cannot fumble them yet. The work begins on vest day.
Vest day: payday in shares
On vest day the promise becomes property. The shares land in your brokerage account, and their total value that day, the share count times the vest-day price, is added to your W-2 as ordinary wages. The IRS treats a $50,000 vest exactly like a $50,000 cash bonus. Equity is salary in a costume, and on vest day the costume comes off for an afternoon.
Because vests are wages, your employer must withhold tax, and since no cash changed hands, the tax comes out in shares. Most companies use sell-to-cover, where the broker sells a slice of your new shares the same day, or net settlement, where the company keeps the slice and deposits the rest. Either way, the federal income tax piece uses the IRS flat rate for supplemental wages: 22%, rising to 37% only on supplemental wages above $1,000,000 in a year. Social Security, Medicare, and state taxes come out of the share value too.
Watch Wei's cliff vest from chapter 2. On his first anniversary, 1,000 shares vest at $50, adding $50,000 to his W-2. His company keeps 220 shares ($11,000, exactly the 22% federal piece; state and payroll taxes would trim a few more) and deposits 780 shares. Wei never touches cash. Many people first learn that their vest was taxed when the share count arrives smaller than they expected.
The gap: 22% withheld, more owed
The flat 22% rate is the seed of the most common RSU surprise. Withholding is a down payment, while your real bill is set by your marginal rate, the tax rate on your last dollar of income. RSU vests stack on top of salary, so they are taxed at your highest rates.
For Wei the gap is small. His $140,000 salary plus a $50,000 vest puts his marginal federal rate at 24%, so the 22% withheld leaves him roughly $1,000 short for the year. That is annoying but survivable.
Maya shows what the same gap looks like at scale. She earns $220,000 in salary, and about $120,000 of RSUs vest each year. Stacked on top of her salary, that vest layer lands in the 32% and 35% federal brackets.
What $120,000 of vest income adds to Maya's federal bill at her bracket.
The federal tax her employer withholds in shares across the year's vests.
Withheld plus gap equals the bill: $26,400 + $14,030 = $40,430.
Her vests create $40,430 of federal tax, her employer withholds $26,400, and the $14,030 difference belongs to the IRS no later than April, with possible underpayment penalties along the way. Her fix is boring and effective: she spreads the gap across her 26 paychecks by having an extra $540 withheld from each one through a revised W-4. The Finvest Tax Playbook works this exact case in its chapter 10 and covers the W-4 mechanics in chapter 11.
Run your own numbers below. The gap grows with income, and it resets every time your vest schedule or the stock price moves.
The sale, and the trap on the 1099-B
The second tax moment is the sale, and it arrives with the most common RSU filing error in the country. The rule itself is friendly: your basis in each vested share is the vest-day price, because you already paid wage tax on that value. When you sell, only the movement since vest is a capital gain or loss.
Ten months after his cliff, Wei sells 600 of his shares at $54. His basis is $50 a share, $30,000 in total, so his real gain is $2,400, taxed as a short-term gain at his 24% rate: $576.
Then the 1099-B arrives. Brokers are not required to report the wage income baked into RSU basis, so many report a cost basis of $0. Tax software obediently computes a $32,400 gain.
| Form 8949, Wei's 600 shares | As the broker reported it | Corrected |
|---|---|---|
| Proceeds | $32,400 | $32,400 |
| Cost basis | $0 | $30,000 |
| Taxable gain | $32,400 | $2,400 |
| Federal tax at 24% | $7,776 | $576 |
Accepting the broker's number means paying tax twice on the same $30,000: once as wages at vest, again as a phantom gain at sale. For Wei that is $7,200 of pure overpayment. The fix is Form 8949, which exists precisely to correct broker-reported basis. Pull the vest confirmation showing your vest-day price, enter the true basis, and the phantom gain disappears. Check this on every single RSU sale you ever report.
Sell or hold: a fresh decision every vest
Once vest-day taxes are paid, the shares are simply yours, identical to shares you could buy with cash this morning. Holding them is therefore a new investment decision, and the Finvest Personal Finance Guide's cash test cuts straight through it: if the company had paid this vest in cash, would you spend all of it on company stock today? For almost everyone the honest answer is no, because your salary, your unvested ladder, and your benefits already ride on this one company.
Selling promptly costs almost nothing in tax. A share sold the day it vests has moved a few cents from its basis, so the capital gain rounds to zero, and the wage tax happened regardless. This is why the same-day autosale setting in your equity portal is the closest thing to a free lunch in this guide. It converts each vest to cash before feelings get a vote, removes the regret window entirely, and leaves your written plan in charge of the money.
Maya's written sell policy, carried over from the Personal Finance Guide, runs her vests on autopilot: sell at least 75% of every vest in the first open window, keep total employer stock under 10% of her investable assets, and write down any exception before the vest date. Her broker's autosale does the selling. Her only vest-week jobs are moving cash to her index funds and topping up the tax set-aside. She says the policy's best feature is the silence: no debate with herself, four times a year.
Closing the gap before April
If you take one action from this chapter, make it this one: estimate this year's withholding gap now. Project the year's vests at today's price, apply your marginal rate, subtract the 22% that will be withheld, and the remainder is a bill already accruing. There are two clean ways to pay it down. The W-4 route adds a flat extra amount to every paycheck's withholding, like Maya's $540, and needs no calendar discipline. The estimated-payments route sends the IRS a check each quarter, which suits people with lumpy vest schedules. The Finvest Tax Playbook covers both routes, including the safe-harbor rules that protect you from penalties while you catch up.
Every January, project the year's RSU vests and the withholding gap at your marginal rate, then close it with a W-4 adjustment or quarterly estimates. Every time you sell, check the 1099-B basis against your vest confirmations before filing. These two habits prevent nearly every RSU disaster.
Where people go wrong
- Trusting the 22%. Withholding is a down payment sized for someone in a lower bracket. Maya's true bill ran $14,030 past it in one year.
- Accepting the 1099-B as printed. A $0 basis taxes the same dollars twice. Keep every vest confirmation and correct the basis on Form 8949.
- Holding every vest by default. It feels like doing nothing, and it is actually a repeated stock purchase that fails the cash test.
- Treating the withheld shares as the whole bill. State tax and the marginal-rate gap remain after the shares are gone.
- Waiting for April. Underpayment penalties accrue during the year. The W-4 fix takes ten minutes in January.
Key takeaways
- RSUs have two tax moments: vest, where the full value becomes W-2 wages, and sale, where gain or loss is measured from the vest-day basis. Grant is tax-free.
- Employers withhold a flat 22% federal on vests. Maya's $120,000 vest year creates $40,430 of federal tax against $26,400 withheld, a $14,030 gap she closes with an extra $540 per paycheck.
- Your basis is the vest-day price. Brokers may report $0; Form 8949 fixes it. Wei's correction turned a $32,400 phantom gain into the true $2,400 and saved $7,200.
- Vested shares are a fresh investment decision. Apply the cash test and make same-day autosale the default.
- Project vests and the withholding gap every January, then fix it through the W-4 or quarterly estimates before penalties start.
Sources: IRS: Publication 525, Taxable and Nontaxable Income · IRS: Publication 550, Investment Income and Expenses · IRS: About Form 8949 · Finvest Tax Playbook · Finvest Personal Finance Guide