How RSUs and ESPPs are taxed, where employees make avoidable mistakes, and how to plan withholding, concentration, and sales.
Definition first
This guide is designed for first-pass understanding. Start with core terms, then apply the framework in your own account workflow.
If you work in tech, finance, or any public company, a chunk of your compensation probably comes in company stock. RSUs and ESPPs can be incredibly valuable — but they're also confusing, weirdly taxed, and dangerous if you let too much of your net worth concentrate in a single stock. Here's how both programs actually work, how they get taxed at every stage, and when it makes sense to sell.
RSUs: Restricted Stock Units
A Restricted Stock Unit is a promise from your employer to give you shares of company stock on a future date, provided you're still employed. RSUs have replaced stock options as the default equity compensation at most large companies because they're simpler: they're always worth something (unlike options, which can be underwater), and the tax treatment is more straightforward.
How RSU Vesting Works
Most RSU grants follow a with a one-year cliff. That means nothing vests for the first 12 months, then 25% of the grant vests at the one-year mark, and the remaining 75% vests in equal installments (usually quarterly or monthly) over the next three years.
four-year vesting schedule
For example, if you receive a grant of 1,000 RSUs:
Month 1-12: 0 shares vested (cliff period)
Month 12: 250 shares vest (25% cliff)
Month 13-48: ~20.8 shares vest per month (remaining 750 over 36 months)
Some companies use different schedules. Amazon famously uses a 5/15/40/40 structure, where only 5% vests in Year 1 and 15% in Year 2, with the bulk backloaded into Years 3 and 4. Google uses a front-loaded schedule. Always read your grant agreement carefully.
How RSUs Are Taxed
RSU taxation happens at two points: vesting and sale.
At vesting: When shares vest, their fair market value on that date is treated as ordinary income. Your company will report this on your W-2, and they'll withhold taxes automatically — usually by selling some of your vesting shares to cover the tax bill (called "sell to cover").
The standard federal supplemental withholding rate is 22% for amounts up to $1 million and 37% for amounts above $1 million. Add state taxes (up to 13.3% in California), Social Security (6.2% up to the $168,600 wage base in 2025), and Medicare (1.45% plus 0.9% surtax above $200,000), and your effective withholding can be 35-50% of the vested value.
Tax Component
Rate
Notes
Federal income tax (withheld)
22%
Flat supplemental rate; may owe more at filing
State income tax
0-13.3%
Varies by state; CA is the highest
Social Security
6.2%
Up to $168,600 wage base (2025)
Medicare
1.45%
+0.9% above $200K single / $250K married
At sale: If you sell your vested shares, any gain or loss relative to the price at vesting is a capital gain or loss. If you sell immediately at vest, there's typically no gain (and thus no additional tax). If you hold and the stock goes up, you'll owe capital gains tax on the appreciation.
Here's an example. You receive 100 RSUs. They vest when the stock is at $150/share. That's $15,000 of ordinary income reported on your W-2. Your company sells 35 shares to cover taxes, leaving you with 65 shares. Six months later, you sell those 65 shares at $170 each. Your capital gain is ($170 − $150) × 65 = $1,300, taxed as a short-term gain since you held less than a year.
The Underwithholding Problem
The 22% flat federal withholding rate is almost always not enough if you're a high-earning tech worker. If your actual marginal federal rate is 32% or 35%, you'll owe the difference at tax time. Many people are surprised by a five-figure tax bill in April because of RSU underwithholding. Plan ahead by making estimated tax payments or adjusting your W-4 withholding.
ESPPs: Employee Stock Purchase Plans
An Employee Stock Purchase Plan lets you buy company stock at a discount, typically 15% off the market price. Most ESPPs follow Section 423 of the tax code, which provides favorable tax treatment if you meet certain holding requirements.
How ESPPs Work
A typical ESPP operates in six-month offering periods. During each period, your employer deducts a percentage of your paycheck (usually up to 10-15%) and accumulates it. At the end of the period, that accumulated cash is used to buy company stock at a discount.
The discount is usually 15% off the stock price, and most plans include a lookback provision: the purchase price is 85% of the lower of the stock price at the beginning or end of the offering period. This means if the stock goes up during the period, your discount is calculated off the earlier, lower price — giving you an even bigger effective discount.
Example: The stock is $100 at the start of the offering period and $120 at the end. With a lookback provision, your purchase price is 85% of $100 = $85/share. You're buying $120 stock for $85 — a 29% effective discount. That's an incredible return on a six-month investment.
The IRS limits ESPP purchases to $25,000 worth of stock per calendar year (based on the fair market value at the start of the offering period). At a 15% discount, you're looking at a guaranteed $3,750 annual gain before any stock price appreciation. This is as close to free money as it gets in personal finance.
ESPP Tax Treatment: Qualifying vs. Disqualifying Dispositions
ESPP taxation depends on when you sell the shares. A qualifying disposition requires holding the shares for both: (1) at least two years from the offering date, and (2) at least one year from the purchase date. Everything else is a disqualifying disposition.
Disposition Type
Ordinary Income Portion
Capital Gain Portion
Qualifying (held 2+ years from offer, 1+ year from purchase)
Lesser of: 15% discount or actual gain
Remainder taxed as long-term capital gain
Disqualifying (sold before holding period)
Spread between purchase price and FMV at purchase
Remainder taxed as short or long-term capital gain
In practice, many financial advisors recommend selling ESPP shares immediately (a disqualifying disposition) because the concentration risk of holding a single stock outweighs the tax benefit of waiting for a qualifying disposition. The discount is your profit — take it, diversify, and move on.
Concentration Risk: The Danger Nobody Talks About
Between RSUs, ESPPs, and your salary, you could easily have 50-80% of your financial life tied to a single company. Your income, your equity compensation, and your invested savings all depend on the same stock going up. If the company hits trouble — layoffs, earnings misses, scandals — you could lose your job AND watch your portfolio crater simultaneously.
Ask former employees of Enron, Lehman Brothers, or more recently, Silicon Valley Bank. Concentration risk is the single biggest financial mistake that equity compensation creates. A general guideline: no single stock should represent more than 10-15% of your total investable assets.
When to Sell RSUs
The default advice — and it's good advice — is to sell RSUs as they vest. Think of it this way: if your employer handed you $15,000 in cash on vesting day, would you walk to your brokerage and buy $15,000 of your company's stock? If the answer is no, you should sell.
Reasons you might hold instead of selling immediately:
You genuinely believe the stock is undervalued and would buy it anyway with your own cash. (Be honest with yourself — this is often anchoring bias.)
You want to hold for long-term capital gains treatment. If you hold for a year after vesting, any further appreciation qualifies for the lower long-term rate. This only makes sense if the diversification risk is manageable.
You're below the concentration threshold. If company stock is 5% of your portfolio, holding a bit longer is less risky than if it's 40%.
The 83(b) Election: For Early-Stage Startups Only
If you receive restricted stock (not RSUs — actual restricted shares) from an early-stage startup, you may be able to file an 83(b) election within 30 days of the grant. This lets you pay ordinary income tax on the stock's current value rather than its (presumably much higher) future value at vesting.
Example: You receive 10,000 restricted shares valued at $0.10 each. Without an 83(b) election, you'd owe tax on the shares' value at vesting — which could be $10 per share if the company has grown, creating a $100,000 tax bill. With the 83(b) election, you pay tax on $1,000 (10,000 × $0.10) upfront, and all future appreciation is taxed as capital gains.
The risk: if you leave the company before vesting and forfeit the shares, you've paid tax on income you never actually received. You can't get a refund. The 83(b) election is a bet that the stock will appreciate and that you'll stay long enough to vest. For early-stage employees with very low current valuations, it's usually worth the gamble.
Critical deadline: You must file the 83(b) election with the IRS within 30 days of receiving the stock. Miss this deadline and there are no do-overs. Mail it certified, keep the receipt, and send a copy with your tax return.
Building a Diversification Plan
Rather than making ad hoc decisions each time shares vest, create a systematic plan:
Set a concentration limit. Decide the maximum percentage of your portfolio that should be in company stock — 10% is a common target.
Sell on a schedule. Sell RSUs as they vest (or within the same week). Sell ESPP shares at purchase or shortly after. Remove emotion from the decision.
Reinvest into diversified funds. Take the proceeds and invest in a broad-market index fund. Your human capital is already concentrated in your employer — your financial capital shouldn't be.
Max out ESPP. The 15% discount is guaranteed return. Always contribute the maximum your budget allows — even if you sell immediately.
Track your cost basis. With RSUs vesting at different prices and ESPP purchases at varying discounts, your cost basis gets complicated quickly. Clarity tracks this automatically when you connect your brokerage accounts.
How Clarity Helps You Manage Equity Compensation
Equity compensation creates a tracking nightmare: multiple vest dates, different cost bases, shares sold to cover taxes, ESPP purchases at varying prices, and wash-sale concerns if you're also tax-loss harvesting. Clarity consolidates all of this into a single dashboard, showing your total company stock exposure as a percentage of your net worth and flagging when concentration risk is getting too high.
What to Do Next
Pull up your equity compensation portal and figure out three things: (1) how many shares are vesting in the next 12 months, (2) what your current company stock concentration is as a percentage of your total investments, and (3) whether you're maxing out your ESPP. If your concentration is above 15%, start building a sell schedule. If you're not enrolled in your ESPP, sign up during the next enrollment window — the guaranteed discount is too good to leave on the table.
This article is for educational purposes and does not constitute tax or financial advice. Consult a CPA or financial advisor for guidance specific to your equity compensation situation.
Try this workflow
Run this framework inside Clarity
Apply this concept with live balances, transactions, and portfolio data instead of static spreadsheets.