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M05 · Module 5 of 11

Equity compensation

Equity compensation is often the largest and most confusing part of a high earner’s pay, and it is taxed in ways that surprise people every spring. This module explains the four common forms of company equity, when each one is taxed, and the planning questions each one raises.

What you’ll take away

  • Tell RSUs, NSOs, ISOs, and ESPP shares apart, and know the exact moment each is taxed.
  • Understand the RSU withholding gap and why it produces a bill at filing.
  • See how ISO exercises can trigger AMT, and what a qualifying disposition changes.
  • Know what an 83(b) election does and the risk it carries.
  • Recognize QSBS eligibility and concentration risk, and where each hands off to a professional.

Four ways companies hand you equity

Companies grant equity to attract and retain people, and to tie pay to the value they help create. There are four forms you are most likely to see, and the differences between them are mostly about when the IRS decides you have received income.

A restricted stock unit (RSU) is a promise to deliver shares once you have earned them, usually by staying employed across a vesting schedule. You pay nothing to receive RSUs. When they vest, the shares are yours and their value is treated as pay.

A non-qualified stock option (NSO) is the right to buy shares at a fixed price, called the strike or exercise price, for a set number of years. The grant gives you the option; you choose whether and when to exercise it.

An incentive stock option (ISO) is also the right to buy shares at a fixed price, but it carries a special tax status available only to employees and only within statutory limits. ISOs are the most tax-favored grant when everything lines up, and the most complicated when it does not.

An employee stock purchase plan (ESPP) lets you buy company shares through payroll deductions, usually at a discount. It is a benefit you opt into rather than a grant you are handed.

Two of these (RSUs and ESPP) involve actual shares. Two (NSOs and ISOs) involve options to buy shares. That distinction drives almost everything that follows, because an option is taxed around the act of exercising, while a share is taxed around the act of receiving or selling it.

RSUs and the withholding gap that surprises people at filing

RSUs are the simplest form to understand and the one most likely to leave you owing money in April.

When RSUs vest, the fair market value of the shares on that day counts as ordinary income, exactly like salary. If 200 shares vest at $150, you have $30,000 of additional wages that year. That amount lands on your W-2, and it becomes your cost basis in the shares. Sell them later for more, and the gain above that basis is a capital gain; sell for less, and you have a capital loss. Selling within a year of vesting makes any gain short-term and taxed at ordinary rates; holding past 1 year (2025 and 2026) makes it long-term and taxed at the lower long-term rate.

So far this sounds clean. The problem is withholding.

Your employer must withhold tax when RSUs vest, just as it does on salary. Equity vesting is treated as supplemental wages, and the default federal withholding on supplemental wages is a flat rate, 22% (2025 and 2026). Most companies meet that obligation by selling a portion of the vesting shares (sell-to-cover) and remitting the proceeds. That sounds like your taxes are handled. For a high earner, they usually are not.

The flat supplemental rate is frequently well below a high earner’s true marginal rate. A large RSU vest stacks on top of an already-large salary, so those dollars are taxed at the top of your stack, which can include the top federal bracket plus the net investment income and Additional Medicare surtaxes and state tax. When the company withholds at the flat supplemental rate but your real marginal rate on that income is meaningfully higher, the difference is deferred to your tax return, not erased. The result is a balance due at filing that can run into the tens of thousands, on income you received as shares months earlier and may already have spent.

The fix is not exotic. You estimate the gap during the year and cover it through additional withholding, a quarterly estimated payment, or by setting the money aside so the April bill is expected rather than alarming. To see the shortfall for your own situation, the RSU withholding gap estimator compares the flat supplemental withholding against your real marginal rate. For the broader question of what an offer actually puts in your pocket after the full tax stack, the equity-comp true take-home calculator translates a gross package into spendable dollars. How your real marginal rate is built up, across brackets, surtaxes, and state tax, is the subject of how AMT fits the full tax stack and your real marginal rate.

How NSOs are taxed when you exercise

Non-qualified stock options are taxed at the moment you exercise them, not when they are granted and not when they vest.

When you exercise an NSO, you buy shares at your strike price while they are worth more on the open market. That difference, market value minus strike price, is the bargain element or spread, and it is taxed as ordinary income in the year you exercise. Exercise an option with a $10 strike when the shares trade at $60, and the $50 per share spread is ordinary income, the same as wages. Because it is treated as compensation, your employer withholds tax on it, and the spread shows up on your W-2.

Your cost basis in the shares becomes the market value on the exercise date (strike plus spread). From there the normal capital-gains rules apply: any further appreciation is a capital gain when you sell, long-term if you hold past 1 year (2025 and 2026) from the exercise date, short-term if not.

Two practical points. First, exercising an NSO usually costs cash twice, once for the strike price and again for withholding on the spread, so a large exercise can require real liquidity. Second, the spread is taxed even though you have not sold anything: you can owe tax on a paper gain in a private company whose shares you cannot easily sell. That mismatch between a tax bill and actual cash recurs across equity comp, and it is worth planning for before you exercise rather than after.

ISOs, AMT, and why timing changes everything

Incentive stock options follow different rules, and the differences are where the planning lives.

When you exercise an ISO, there is no regular income tax on the spread. That is the headline benefit: you can buy shares well below market value without triggering ordinary income the way an NSO would. If you then hold the shares long enough and sell, the entire gain over your strike price can be taxed at long-term capital-gains rates rather than ordinary rates. Holding long enough means a qualifying disposition, defined by two clocks that must both run: at least 2 years (2025 and 2026) from the grant date and at least 1 year (2025 and 2026) from the exercise date. Meet both, and the favorable treatment applies. Sell before either clock runs (a disqualifying disposition), and some or all of the spread is pulled back into ordinary income, much as if it had been an NSO.

There is a catch that catches people, and its name is the alternative minimum tax.

The alternative minimum tax (AMT) is a parallel tax system. You compute your tax the normal way, compute it again under AMT rules, and pay whichever is higher. AMT runs on a broader income base, allows fewer deductions, applies its own rate, and shelters part of your income with an exemption that phases out as income rises. The reason it matters here: although the ISO spread is invisible to the regular tax system at exercise, it is a preference item added back under AMT. Exercise a large block of ISOs in private-company shares you cannot sell, and you can generate a substantial AMT bill on a paper gain, with no shares sold and no cash raised to pay it. This is the same tax-without-cash mismatch as NSOs, sharpened, because the trigger is the exercise itself.

The size of an ISO exercise therefore changes its tax character. A small exercise may stay under the AMT threshold and cost nothing currently; a large one in the same year can tip you into AMT. Spreading exercises across calendar years, or sizing an exercise to stay within your AMT headroom, is a common way people manage this, and it turns on your specific numbers. AMT triggered by an ISO exercise often generates a credit you can recover against regular tax in later years, which softens the cost over time without removing the cash-flow problem in the year you exercise.

This module covers the AMT interaction at the level you need to make sense of an ISO exercise. How AMT sits inside your full tax stack, alongside the regular brackets and surtaxes, and how it shapes your real marginal rate, belongs to how AMT fits the full tax stack and your real marginal rate. To estimate the tax cost and timing of a specific exercise, use the ISO exercise tax-impact simulator; to estimate whether an exercise tips you into AMT and by how much, use the AMT exposure estimator. The simulators compute your situation; the decision about how many to exercise and when is a personal one, and that is where a CFP comes in.

ESPP and the qualifying-disposition discount

An employee stock purchase plan lets you set aside payroll dollars over an offering period and buy company stock at a discount. A tax-qualified plan can offer a discount off the share price up to a statutory cap, 15% (2025 and 2026), and the better plans add a lookback that prices your purchase off the lower of the price at the start or the end of the offering period. The discount and the lookback together can make an ESPP one of the highest-return benefits available to an employee.

The taxation depends on how long you hold the purchased shares, and the two-clock pattern returns. A qualifying disposition requires holding the shares at least 1 year (2025 and 2026) from the purchase date and at least 2 years (2025 and 2026) from the start of the offering period. Meet both, and the tax treatment is favorable: a portion of your gain (roughly the discount) is ordinary income and the rest is long-term capital gain. Sell sooner, and you have a disqualifying disposition: the full discount measured at purchase becomes ordinary income, and the remaining gain is a capital gain that is short- or long-term depending on your holding period.

The discount is real money either way; the holding period only changes how the gain is split between ordinary and capital rates. Many people weigh the tax benefit of holding against the concentration risk of accumulating still more employer stock, which the final section takes up.

An 83(b) election and early-exercise decisions

Some plans let you exercise options before they vest (an early exercise), and some grants come as restricted stock rather than options. In both cases you may hold shares that are not yet fully yours because they remain subject to vesting. That creates a choice about when you are taxed, and the tool for making it is the 83(b) election.

By default, restricted shares are taxed as ordinary income on their value at vesting. If the company grows, that value can be far higher than when you received the shares, and your tax bill grows with it. A Section 83(b) election lets you choose to be taxed now instead, on the value at the time you receive or early-exercise the shares, before the company has appreciated. You must file it with the IRS within 30 days (2025 and 2026) of the grant or exercise; the window is short and unforgiving.

When the value today is very low (early-stage startup shares, or an early exercise where strike and market value are nearly equal), the election can mean paying tax on almost nothing now, converting future appreciation into capital gain instead of ordinary income, and starting your long-term holding clock early. That can be a large benefit if the company succeeds.

It carries a real risk. You pay tax up front on shares that may never be worth anything. Leave before vesting or watch the company fail, and you generally do not get that tax back, having possibly also spent cash to exercise shares that became worthless. An 83(b) election is a bet that the equity will pay off, made with your own money on a tight deadline. To model the tradeoff for a specific grant, the 83(b) election decision modeler compares paying tax now against paying it at vesting. Whether to make that bet is a personal decision for you and a CFP.

QSBS and the founder-stock exclusion

Some company stock qualifies for one of the most favorable provisions in the tax code: the qualified small business stock (QSBS) exclusion under Section 1202. For founders and early employees of a startup, it can turn a large gain into a largely or entirely tax-free one.

In broad terms, stock can be QSBS if it is stock of a domestic C corporation (not an S corporation or an LLC), acquired at original issuance (not bought from another shareholder), while the company’s assets were under a size cap, $75,000,000 (2025 and 2026), and the company is in a qualifying line of business. Meet those conditions and hold the stock for at least 5 years (2025 and 2026), and you can exclude gain on a sale up to the greater of a fixed dollar cap, $15,000,000 (2025 and 2026), or a multiple of your basis, 10x (2025 and 2026). For early employees with low-basis founder-class shares, the exclusion can cover a substantial gain.

QSBS is shared with the business module because it depends on how the company is structured and capitalized, decisions usually made on the owner’s side. As an employee holding what might be QSBS, what matters most is whether the stock is C-corp stock acquired at issuance and whether your holding clock has run. To check eligibility and estimate the exclusion, use the QSBS exclusion calculator. For how eligibility is engineered from the company’s side, see QSBS as it applies to C-corp business owners. Eligibility is technical and fact-specific, so confirming a real position is work for a tax professional rather than a self-assessment.

When one stock becomes too much of your net worth

Equity compensation does its job too well in one specific way: it concentrates your wealth in a single company, the same company that already pays your salary. Your job, your income, and a large share of your savings can all ride on one stock. If that stock falls, you can lose your net worth and your income at the same time.

Concentration is a risk question, and risk pulls against taxes. Selling concentrated shares usually triggers a tax bill, a real reason people hold. Holding to defer tax is also how single positions grow to dominate a portfolio. A useful frame: decide how much single-stock exposure you are willing to carry as a share of your net worth, treat that as a ceiling, and diversify the excess on a schedule rather than trying to time the stock. The discipline is in pre-committing to the rule, because selling a winner is hard in the moment.

Selling can be constrained by more than taxes. Employees with access to material non-public information, and corporate insiders, often cannot trade whenever they like. A 10b5-1 plan is a written trading plan, set up in advance while you are not aware of inside information, that sells shares automatically on a preset schedule or set of price triggers. Because it is established ahead of time, it lets insiders diversify steadily without making a trading decision on any given day. The schedule does the selling; you are not choosing the moment.

How much to hold, how fast to sell, and how to sequence sales against your tax situation are personal decisions that depend on your full picture. The platform’s role is to make the exposure concrete and show the framework. The concentrated-position analyzer quantifies what share of your net worth sits in one stock and models how diversifying changes your risk. Fitting a concentrated position into a diversified portfolio is covered in diversifying a concentrated position inside your portfolio. If you are charitably inclined, donating appreciated shares can reduce concentration and your tax bill in one move, covered in donating appreciated shares to address giving and concentration at once. The specific “how much, and when” for you is a decision for a CFP.

Putting it together

Equity compensation comes in four forms, and the first question for any of them is when it is taxed. RSUs are taxed as ordinary income at vesting, and the flat supplemental withholding often falls short of a high earner’s real rate, leaving a gap to cover at filing. NSOs are taxed as ordinary income on the spread when you exercise. ISOs avoid regular tax at exercise but can trigger AMT on the spread, and a qualifying disposition unlocks long-term capital-gains treatment. ESPP shares carry a discount, and the qualifying-versus-disqualifying-disposition rules decide how the gain is split. An 83(b) election lets you choose to be taxed early while the value is low, a bet that pays off only if the equity does. QSBS can exclude a large gain on qualifying C-corp stock held long enough. Across all of it, watch concentration: equity that performs well can quietly become most of your net worth. The tools compute your situation; the personal decisions hand off to a CFP.

Connections

This module explains how these strategies work. For what to do in your own situation, the platform hands off to a CFP.