Your offer letter says $180,000 in restricted stock units over four years. You do the mental math — $45,000 a year on top of salary — and picture what that buys. Then your first vesting date arrives, a chunk of shares lands in your brokerage account, most of them instantly vanish to cover taxes, and the following April you still owe the IRS several thousand dollars more. Nothing went wrong. That is simply how RSUs work, and almost nobody explains it before you sign.
This guide covers what RSUs actually are, when tax hits, why the default 22% withholding leaves higher earners short, how double-trigger vesting works at private startups, why there is no 83(b) election for RSUs, and the cost-basis trap that causes people to pay tax on the same income twice.
What an RSU Actually Is: A Promise, Not Stock
A restricted stock unit is your employer's contractual promise to deliver shares (or their cash value) once conditions are met. At grant, you own nothing. You cannot vote the shares, receive dividends on them (though some plans pay dividend equivalents), or sell them. You hold a bookkeeping entry that converts into real shares later.
This matters for two reasons. First, because no property transfers at grant, there is nothing to tax yet — the IRS waits until the promise is fulfilled. Second, it is what separates RSUs from restricted stock awards, where actual shares change hands up front subject to forfeiture. That distinction drives the entire tax treatment, including why one gets an 83(b) election and the other does not.
For employers, RSUs are simple: no purchase price to administer, no option exercise window to manage, and the award always retains some value as long as the stock is worth anything. For you, the trade-off is less control over timing — you are taxed when shares arrive, whether or not you would have chosen to buy stock that day.
The Four Dates That Matter: Grant, Vest, Settle, Sell
Confusion around RSUs usually comes from blurring four separate events:
Grant date. The company awards you a number of units subject to a vesting schedule. No tax. No shares. Just paperwork and a number in your equity portal.
Vesting date. Your conditions are satisfied and the company's obligation becomes unconditional. This is the big one: vesting is generally the tax event. The fair market value of the shares on this date is ordinary compensation income to you, reported on your W-2, subject to federal and state income tax plus Social Security and Medicare.
Settlement date. The company actually delivers shares or cash, usually within days of vesting and almost always in the same tax year. Some deferred-settlement plans push delivery later, but the taxable amount is still fixed by the value at vesting.
Sale date. You sell shares on the market. Tax here depends on what happened since vesting: any change in price between vesting and sale is a capital gain or loss, short-term or long-term depending on how long you held after vesting.
A concrete example: you are granted 2,000 RSUs when the stock trades at $22. They vest 25% per year. In year one, 500 shares vest when the stock is worth $30. You recognize $15,000 of ordinary income (500 × $30), your employer withholds taxes from it, and your cost basis in those 500 shares becomes $30 each. If you later sell at $40, the extra $10 per share is capital gain — not a second round of compensation income.
Vesting Schedules: Cliffs, Graded Vesting, and Double Triggers
Most public-company RSUs vest on time-based schedules: a one-year cliff (nothing vests until you complete twelve months, then 25% lands at once) followed by monthly or quarterly graded vesting over the remaining three years. Leave before a tranche vests and you forfeit it — the "golden handcuffs" are the point.
Private startups often add a second condition, called double-trigger vesting. Your shares vest only when both triggers fire:
- Time-based service condition — you stay the required years, same as normal.
- Liquidity event condition — the company goes public or is acquired.
Until both occur, you have no shares and owe no tax, which protects you from the nightmare of owing income tax on illiquid private shares you cannot sell. The catch is forfeiture risk: if you leave before an IPO, time-vested units typically expire unvested — commonly within a few months to a few years after departure, depending on the plan. Some companies extend post-termination exercise or settlement windows, but many do not. Before joining a pre-IPO company, ask how long time-vested units survive your departure and what happens if the liquidity event never comes.
Taxes: Vesting Day Is Payday in the IRS's Eyes
Here is the rule to internalize: with RSUs, vesting is (almost always) the first and largest tax event, not the sale. The value delivered at vesting is supplemental wages — taxed as ordinary income at your marginal rate, just like a cash bonus.
That income shows up on your W-2 with federal, state, Social Security, and Medicare withholding. Your per-share cost basis going forward equals the amount you already paid tax on: the market value at vesting. Keep records of every vesting-date value, because your broker will not do it for you (more on that trap below).
One more wrinkle for startup employees: if your company is private and settles RSUs in shares with no market, the plan may use net settlement or a sell-to-cover at IPO to handle the tax bill. Either way, budget as though a third or more of each vesting tranche belongs to the government from day one.
The 22% Withholding Gap: Why You Still Owe in April
Employers withhold on RSU income under the IRS supplemental-wage rules: a flat 22% federal rate on supplemental wages up to $1 million in a calendar year, and a mandatory 37% on amounts above $1 million. States add their own flat supplemental rates on top.
The gap that burns people: 22% is a withholding convenience, not your tax rate. If your combined salary plus RSU income puts you in the 32%, 35%, or 37% bracket, every vested dollar above the 24% bracket line was under-withheld by 10 to 15 percentage points. A $50,000 vesting tranche withheld at 22% when your marginal rate is 35% leaves a $6,500 shortfall you discover at filing time — plus possible underpayment penalties if the gap is large enough across the year.
Three ways employers collect the withholding, and what each means for you:
- Sell-to-cover (most common). The company sells just enough of your newly vested shares to pay the withholding and deposits the rest in your account. You keep fewer shares than vested — expect roughly a quarter to half to disappear at higher incomes.
- Net settlement. The company withholds whole shares instead of selling them. Economically identical to sell-to-cover; you simply never see the withheld shares.
- Cash payment. You write the employer a check (or take a payroll deduction) and keep all shares. Rare, and only sensible if you have spare cash and want maximum share exposure.
If RSUs are a meaningful part of your pay, fix the gap during the year rather than at filing: raise regular W-4 withholding, make estimated quarterly payments, or both. The one scenario where the gap narrows on its own is a very large vesting year — once cumulative supplemental wages cross $1 million, the mandatory 37% withholding on the excess usually covers (or over-covers) the actual liability.
Why There Is No 83(b) Election for RSUs
Employees who have heard of the 83(b) election — the maneuver that lets founders and early hires pay tax up front on cheap restricted stock so later appreciation is capital gain — often ask how to file one for RSUs. The answer is you cannot, and the reason is structural.
An 83(b) election applies when property is transferred subject to forfeiture. Restricted stock qualifies because real shares change hands on day one. RSUs do not, because at grant you receive only an unfunded promise — no stock has been issued, so there is no property to elect on. Tax law taxes the compensation when the shares actually arrive at vesting, at whatever they are worth then.
Do not confuse this with the Section 83(i) qualified-equity-grant deferral, a separate and narrower rule that lets some private-company employees defer (not eliminate) tax on RSU settlement for up to five years under strict conditions, including employer opt-in and escrow requirements. It helps with the illiquidity problem in limited cases; it is not an 83(b) by another name, and most employees at most companies will never be eligible.
Selling: Holding Periods and the Basis Trap That Double-Taxes People
After vesting, your shares are just shares. Sell immediately and there is little or no additional gain — many advisors treat "sell at vest, diversify the proceeds" as the default. Hold, and every dollar of movement becomes capital gain or loss: short-term (taxed as ordinary income) if you sell within a year of vesting, long-term (taxed at preferential rates) if you hold more than a year after vesting.
Now the trap. When you sell, your broker issues Form 1099-B reporting the sale proceeds — but brokers frequently report the cost basis of RSU shares as $0 or omit it, because they never tracked the compensation income you already paid tax on. If you copy the 1099-B into your return unadjusted, you pay tax on the full sale price — taxing the same dollars twice. The fix: manually adjust the basis to the vesting-date fair market value (the amount already on your W-2), and keep every vesting confirmation and pay stub until the shares are sold plus the statute of limitations runs. Reconcile each sale lot against its vesting lot; with quarterly vesting over four years, that is up to sixteen lots to track.
Common RSU Mistakes and How to Avoid Them
- Treating the grant-date value as locked in. Your offer letter's dollar figure used the stock price that day. If the stock falls 40%, so does your award. Evaluate offers on share count and vesting terms, not headline value.
- Ignoring concentration risk. Salary, bonus, unvested RSUs, and vested-but-held shares can leave 80% of your net worth riding on one company — the same company that decides whether you stay employed. Set a rule in advance (for example, sell at vest above a target allocation) and follow it mechanically.
- Forgetting state taxes. Moving between states between vesting tranches can split the income across jurisdictions. High-tax states source RSU income by workdays during the vesting period, not by where you live at sale. Track work locations if you relocate mid-vest.
- Letting double-trigger units expire. Departing a startup with time-vested but untriggered RSUs starts a forfeiture clock. Calendar the expiration date on your last day, not "sometime later."
- Assuming the 83(b) or 83(i) will save you. One does not apply to RSUs at all; the other requires your employer to offer it and you to meet every condition. Plan for ordinary income at vesting unless both are confirmed in writing.
- Paying estimated-tax penalties. A big vesting year with 22% withholding can trigger underpayment penalties. Annualize the shortfall early and true it up with estimated payments or W-4 adjustments.
What to Do at Each Stage
At grant: screenshot the award agreement, vesting schedule, settlement timing, and post-termination forfeiture rules. Ask private-company employers about the liquidity trigger and expiration window in writing.
At each vest: record the date, share count, and fair market value; confirm the W-2 reflects the income; check whether withholding covered your marginal rate and top up with estimated payments if not.
At sale: match every lot sold to its vesting-date basis, correct the 1099-B, and classify gains by holding period measured from vesting — not from grant.
Every year: revisit concentration. RSUs that performed well create exactly the problem success brings: too much of your wealth in one ticker. Rebalancing is not disloyalty; it is the reason equity compensation exists — to build wealth you actually keep.
Keep Your Equity Records Organized From Day One
RSUs reward employees who track four dates, sixteen lots, and a basis the broker will not track for them — which is another way of saying they reward good bookkeeping. Keep a simple ledger of every grant, vesting value, withholding amount, and sale, and reconcile it against your W-2 and 1099-B each spring. Beancount.io provides plain-text accounting that gives you complete transparency and control over your financial data — no black boxes, no vendor lock-in. Get started for free and see why developers and finance professionals are switching to plain-text accounting.
