How are long term capital gains taxes calculated?
You pay taxes on capital gains when you realize your gains by selling the investment property.  Also, in the US, taxes on capital gains are computed at special rates depending on your current income level, and so when you realize your gains two years from now, you will pay taxes on the gains at the special rate then applicable to your income level for the year of sale. Remember also that the US Congress  can change the tax laws at any time between now and the time you sell your stocks, and so the rates you are looking at now may have changed too. Capital gains taxes for a year are calculated on sales of assets that take place during that year.  So if you sell some stock in 2016, you will report those gains/losses on your 2016 tax return.
"The reason is that although the American economy is functioning normally, mortgage rates are stupid-low, and are below a prudent expectation of long-term (30 year) rates of return in the market.   I manage endowments, so I say ""prudent"" in the context of endowment investment, which is the picture of caution and subject to UPMIFA law (the P being prudent).    What's more, there are tax benefits.  Yes, you pay 15% long-term capital gains tax on investment income.  But your mortgage interest is tax deductible at your ""tax bracket"" rate of 25, 28 or 33% - this being the tax you would pay on your next dollar of earned income.  And in the early years of a mortgage, mortgage payments are nearly 100% interest.  So even if it's a wash: you gain $10k in the market but pay $10k in mortgage interest -- you pay $1500 tax on the gains, but the interest deduction redudes tax by $2800. So you are still $1300 ahead.   TLDR: the government pays us to do this." Does this technically mean that she has to pay AMT on $400,000? Yes. Well, not exactly 400,000. She paid $1 per share, so 390,000. And if so, is %28 the AMT for this sum? (0.28 * $400,000 = $112,000)?   Or does she have to include her salary on top of that before   calculating AMT? (Suppose in the fake example that her salary is   $100,000 after 401k). All her income is included in calculating the AMT, minus the AMT exemption amount. The difference between the regular calculated tax and the calculated AMT is then added to the regular tax. Note that some deductions allowed for the regular calculation are not allowed for the AMT calculation. How does California state tax come into play for this? California has its own AMT rules, and in California any stock option exercise is subject to AMT, unless you sell the stock in the same year. Here's a nice and easy to understand write up on the issue from the FTB. When would she have to pay the taxes for this huge AMT? Tax is due when income is received (i.e.: when you exercise the options). However, most people don't actually pay the tax then, but rather discover the huge tax liability when they prepare to submit their tax return on April 15th. To avoid that, I'd suggest trying to estimate the tax and adjust your withholding using form W4 so that by the end of the year you have enough withheld. Suppose in the worst case, the company goes completely under. Does she   get her massive amounts of tax back? Or if it's tax credit, where can   I find more info on this? That would be capital loss, and only up to $3K a year of capital loss can be deducted from the general income. So it will continue offsetting other capital gains or being deducted $3K a year until it all clears out. Is there any way to avoid this tax? (Can she file an 83b election?) You asked and answered. Yes, filing 83(b) election is the way to go to avoid this situation. This should be done within 30 days of the grant, and submitted to the IRS, and a copy attached to the tax return of the grant year. However, if you're considering exercise - that ship has likely sailed a long time ago. Any advice for Little Susie on how she can even afford to pay that   much tax on something she can't even sell anytime soon? Don't exercise the options? Should she   take out a loan? (e.g. I've heard that in the extreme case, you can   find angel investors who are willing to pay all your taxes/strike   price, but want 50% of your equity? I've also heard that you can sell   your illiquid shares on SecondMarket?) Is she likely to get audited by IRS for pulling something like this? You can take a loan secured by shares you own, there's nothing illegal in it. If you transfer your shares - the IRS only cares about the taxes being paid, however that may be illegal depending on the terms and the conditions of the grant. You'll need to talk to a lawyer about your situation. I suggest talking to a licensed tax adviser (EA/CPA licensed in your State) about the specifics concerning your situation. One of the main tax loopholes more readily available to the wealthy in the U.S. is the fact that long-term capital gains are taxed at a much lower rate. Certainly, people making less than $250,000/year can take advantage of this as well, but the fact is that people making, say, $60,000/year likely have a much smaller proportion of their income available to invest in, say, indexed mutual funds or ETFs. You may wish to read Wikipedia's article on capital gains tax in the United States. You can certainly make the argument that the preferential tax rate on capital gains is appropriate, and the Wikipedia article points out a number of these. Nevertheless, this is one of the main mechanisms whereby people with higher wealth in the U.S. typically leverage the tax code to their advantage. This answer fills in some of the details you are unsure about, since I'm further along than you. I bought the ESPP shares in 2012.  I didn't sell immediately, but in 2015, so I qualify for the long-term capital gains rate. Here's how it was reported: The 15% discount was reported on a W2 as  it was also mentioned twice in the info box (not all of my W2's come with one of these) but also  This showed the sale trade, with my cost basis as the discounted price of $5000. And for interests sake, I also got the following in 2012: WARNING! This means that just going ahead and entering the numbers means you will be taxed twice! once as income and once as capital gains. I only noticed this was happening because I no longer worked for the company, so this W2 only had this one item on it. This is another example of the US tax system baffling me with its blend of obsessive compulsive need for documentation coupled with inexplicably missing information that's critical to sensible accounting. The 1099 documents must (says the IRS since 2015) show the basis value as the award price (your discounted price).   So reading the form 8949: Note: If you checked Box D above but the basis reported to the IRS was   incorrect, enter in column (e) the basis as reported to the IRS, and   enter an adjustment in column (g) to correct the basis. We discover the number is incorrect and must adjust.  The actual value you need to adjust it by may be reported on your 1099, but also may not (I have examples of both). I calculated the required adjustment by looking at the W2, as detailed above. I gleaned this information from the following documents provided by my stock management company (you should the tax resources section of your provider): This will work as intended, but there's another point to consider. In the US, the tax rate on proceeds from stock sales is higher for short term holdings, which are defined as held for less than one year. Both rates vary based on your income. Bracket numbers are for fiscal year 2014, filing as single. The difference between short and long term capital gains tax in the US is a minimum of ten percentage points, and works out to 15 percentage points on average. This is substantial. If you won't be reporting much income the year you move to the US (say because you only worked for a portion of the year) it is decidedly to your advantage to wait and sell the stocks in the US, to get that sweet 0% rate. At a minimum, you should hold the position for a year if you sell and rebuy, from a tax optimization perspective. Two caveats: Assuming that what you want to do is to counter the capital gains tax on the short term and long term gains, and that doing so will avoid any underpayment penalties, it is relatively simple to do so. Figure out the tax on the capital gains by determining your tax bracket. Lets say 25% short term and 15% long term or (0.25x7K) + (0.15*8K) or $2950.  If you donate to charities an additional amount of items or money to cover that tax. So taking the numbers in step 1 divide by the marginal tax rate $2950/0.25 or $11,800.  Money is easier to donate because you will be contributing enough value that the IRS may ask for proof of the value, and that proof needs to be gathered either before the donation is given or at the time the donation is given. Also don't wait until December 31st, if you miss the deadline and the donation is counted for next year, the purpose will have been missed. Now if the goal is just to avoid the underpayment penalty, you have two other options.  The safe harbor is the easiest of the two to determine. Look at last years tax form. Look for the amount of tax you paid last year. Not what was withheld, but what you actually paid. If all your withholding this year, is greater than 110% of the total tax from last year, you have reached the safe harbor. There are a few more twists depending on AGI Special rules for farmers, fishermen, and higher income taxpayers.   If at least two-thirds of your gross income for tax year 2014 or 2015   is from farming or fishing, substitute 662/3% for 90% in (2a) under   the General rule, earlier. If your AGI for 2014 was more than $150,000   ($75,000 if your filing status for 2015 is married filing a separate   return), substitute 110% for 100% in (2b) under General rule ,   earlier. See Figure 4-A and Publication 505, chapter 2 for more   information. It turns out that in this special case for New York, they have a law that says that if you are changing your filing status from resident to nonresident, you must use the accrual method for calculating capital gains. So in this case, the date on the papers is the important one. E.g. I buy 1 stock unit for $100.00 and sell it later for $150.00 => income taxes arise. Correct. You pay tax on your gains, i.e.: the different between net proceeds and gross costs (proceeds sans fees, acquisition costs including fees). I buy 1 stock unit for $150.00 and sell it later for $100.00 => no income taxes here. Not correct. The loss is deductible from other capital gains, and if no other capital gains - from your income (up to $3000 a year, until exhausted). Also, there are two different tax rate sets for capital gains: short term (holding up to 1 year) and long term (more than that). Short term capital gains tax matches ordinary income brackets, whereas long term capital gains tax brackets are much lower.