Got RSUs, ISOs, or ESPP? Three different tax surprises are coming. Here's how to dodge them.

All three are ways tech (and finance) companies pay you in stock instead of cash. RSU = Restricted Stock Unit — your company gives you shares for free as part of your salary; you owe income tax on their value when they 'vest' (become yours). ISO = Incentive Stock Option — your company gives you the RIGHT to buy shares at a set 'strike' price (e.g., $10) even if they're worth more (e.g., $50); you exercise when you want. ESPP = Employee Stock Purchase Plan — your company lets you buy company stock with paycheck deductions, usually at a 10-15% discount. Each has totally different tax rules. Most tech employees overpay because they don't realize the rules differ.

Meet Maya. She's a senior engineer at a tech company. This year three things happened: (1) RSUs worth $200,000 vested. Her company withheld federal tax at the 22% supplemental rate ($44,000) but Maya is actually in the 37% bracket — so she's UNDER-withheld by 15% × $200,000 = $30,000. She'll owe that $30,000 in April unless she fixes withholding now. (2) She exercised 1,000 ISOs at $10 strike when the stock was worth $50, then HELD the shares (didn't sell). The $40,000 'bargain element' (FMV − strike) doesn't appear on her W-2 — but it triggers AMT, costing her an extra $10,000 in federal tax this year. (3) She bought $25,000 of stock through ESPP at a 15% discount = $3,750 of extra ordinary income reported when she sells. Total tax surprises: $43,750 she didn't see coming. The calculator below catches all three before April.

Because the IRS gives them a shortcut. RSU vests are 'supplemental wages' — your employer is allowed to withhold federal tax at a flat 22% (or 37% on amounts over $1M in a single year) regardless of your actual tax bracket. If you're in the 24% / 32% / 35% / 37% bracket, that 22% flat rate is too low. Example: $300,000 of vesting RSUs withheld at 22% = $66,000 sent to the IRS. But if your real federal rate is 35%, you actually owe $105,000 federal tax on that vest = $39,000 short. Most employees don't notice until they get the tax bill in April. THE FIX: log into your payroll system, increase your W-4 'extra withholding' amount per paycheck to cover the gap, OR send a quarterly estimated tax payment for the difference.

AMT is the 'Alternative Minimum Tax' — a parallel tax system Congress built in the 1960s to make sure high earners with lots of deductions still pay something. You compute your tax two ways (regular tax and AMT) and pay whichever is HIGHER. ISOs are weird because they don't show up on your W-2 when you exercise — but AMT pretends they did. The 'bargain element' (FMV at exercise minus strike, times shares) is added to your AMT income. Example: you exercise 1,000 ISOs with $10 strike when the stock is worth $50. Bargain element = $40,000. Your regular tax doesn't change, but your AMT income jumps $40,000 — at the 26% AMT rate, that's $10,400 of extra tax. THE FIX: don't exercise ISOs in chunks that push AMT way past your regular tax. Many people exercise in pieces over multiple years to stay just under AMT, OR exercise then immediately sell (a 'disqualifying disposition' which makes it a regular W-2 wage and avoids AMT entirely — but you pay ordinary rates, not LTCG).

Both relate to how long you held the ESPP shares before selling. QUALIFYING disposition: held more than 2 years from the GRANT date AND more than 1 year from the PURCHASE date. Tax treatment: the discount portion (e.g., 15% off) is ordinary income, and any further appreciation is LONG-TERM capital gain (15-20% rate). DISQUALIFYING disposition: sold sooner. Tax treatment: the FMV-at-purchase minus what-you-paid IS ordinary income (potentially MORE than the simple 15% discount, if the stock went up between offering date and purchase date), and any gain after that is short or long-term cap gain. The math gets weird — sometimes a disqualifying disposition costs you more in ordinary income but less in cap gains, sometimes the opposite. For most stocks the qualifying period is the better deal because more of the profit gets cap gains rates.

Almost always YES. Here's why: an RSU vest at $50/share is taxed identically to a $50/share cash bonus PLUS using that cash bonus to buy company stock. So holding vested RSUs is mathematically identical to going to your bank, withdrawing the cash, and buying your employer's stock with it. Most financial advisors would tell you that's a terrible diversification strategy — your salary already depends on the company, why double down with all your savings too? The 'sell at vest' approach: every quarter when shares vest, immediately sell the after-tax shares and reinvest in a diversified portfolio (S&P 500 ETF, target-date fund, whatever you'd otherwise own). Companies don't penalize you for this and most have built-in 'sell-to-cover' automation. The only common counter-argument: if you're at a private company pre-IPO, you may not be able to sell. Once it goes public, sell.

This is the classic ISO trap. Example: you exercise 5,000 ISOs at $10 strike when the FMV is $80, paying $50,000 to exercise. Bargain element: $350,000. AMT: ~$90,000 owed. You hold for the LTCG treatment. Then the stock craters to $5/share. Now your shares are worth $25,000 — but you owe $90,000 in AMT cash. The IRS doesn't care that your stock tanked. THE FIX (do this BEFORE December 31 of the exercise year): if the stock has fallen from your exercise price within the same calendar year, you can do a 'disqualifying disposition' — sell the shares before year-end, which RETROACTIVELY converts the ISO exercise to a non-ISO exercise, kills the AMT, and re-treats it as ordinary W-2 income on the actual realized profit. You still owe tax, but only on what you actually made, not the phantom gain that disappeared. This is the single most important rule about ISOs: if the stock falls below your exercise FMV, sell before December 31 to escape the AMT.

DIY is fine for RSU and ESPP — they're reported cleanly on your W-2 and 1099-B. ISO exercises are where things get tricky enough that a CPA who specializes in tech employees is usually worth the $500-$1500 fee, especially in the year you exercise. Look for one who explicitly mentions 'AMT planning' on their site. They'll model your tax both ways and can help you decide between exercising in pieces, exercising then immediately selling, or waiting. Once you've done it once with a CPA, future years are easier to DIY because the pattern is set. The IRS forms involved: Form 6251 (AMT), Form 3921 (ISO exercise notice your company sends you), Form 3922 (ESPP purchase notice). Tax software handles all three but asks weirdly worded questions — read the help text carefully.