What are Capital Gains?

Capital gains tax planning comes down to two levers you can actually control: your cost basis and your holding period. Tax loss harvesting can reduce taxes today, but it can also reset cost basis in a way that increases future capital gains taxes, so it should be used intentionally, not automatically. High earners should also watch for the 3.8% net investment income tax (NIIT), which can stack on top of capital gains in the right income ranges. Last updated: February 18, 2026.

Capital gains are simple in theory and expensive in real life.

If you are a tech high earner, capital gains can show up in big, lumpy ways. A concentrated stock position runs up. An IPO hits. An acquisition closes. RSUs stack on top of salary. Suddenly, you are not just investing. You are managing tax timing.

In this guide, we are going to make capital gains feel controllable. You will learn the two variables that drive the tax outcome, how tax loss harvesting really works, and how to think about the trade off between “saving taxes now” and “paying more later.”

Capital gains are the profits from investments when you sell for more than you paid. That is the clean definition.

The planning reality is that capital gains are one of the largest moving parts in a high earner’s tax bill, because they are tied to decisions. When you sell, what you sell, and what you sell it for can matter as much as what you earn on your W-2.

Capital gains taxes are influenced by many things, but two inputs do most of the work.

• Cost basis: what you paid for the investment, adjusted for certain events. Cost basis is the starting line for the tax calculation.
• Holding period: how long you held the investment before selling. Holding period determines whether the gain is short-term or long-term.

If you want a broader primer on definitions, start here: What are Capital Gains?.

Short-term capital gains are generally gains on assets held for one year or less. They are typically taxed at ordinary income tax rates, which is why they can be painful for high earners.

Long-term capital gains are generally gains on assets held for more than one year. They are typically taxed at preferential federal rates that depend on taxable income, and high earners may also face additional taxes layered on top.

Planning implication: if you are close to the one-year mark, the decision to sell today versus in a few weeks can change the tax character of the gain. That does not mean you should ignore portfolio risk. It means you should know the size of the tax delta before you choose.

High earners should also be aware of the 3.8% net investment income tax (NIIT), which may apply to investment income, including capital gains, depending on your income and filing situation.

If NIIT is part of your picture, it is not just “a small extra tax.” It can materially change the after-tax outcome of a large sale.

For a deeper read, see: A Comprehensive Guide to NIIT for High-Income Earners.

Tax loss harvesting is one of the most useful tools in a high earner’s tax toolkit. It can also be misunderstood.

Used well, it can reduce taxes and create flexibility. Used blindly, it can reset your cost basis in a way that increases future taxes, especially if you harvest losses in a stock you plan to hold long term.

Tax loss harvesting generally means selling an investment at a loss so the realized loss can offset realized gains elsewhere. Depending on your situation, losses may also offset a limited amount of ordinary income, and unused losses may carry forward.

The key phrase is “realized.” Nothing happens for tax purposes until you sell.

If you want the deeper strategy playbook, read: Harvesting Tax Losses to Beat Capital Gains and Down Market Tactics: A Modern Investor’s Guide to Tax Loss Harvesting.

The part most people miss is this: harvesting a loss can reset your cost basis lower.

A lower cost basis can be great if your goal is to reposition into a different investment with stronger expected returns or better diversification. It can be less great if your goal is simply to “stay in the same stock forever,” because a lower cost basis can mean larger capital gains later when the stock recovers.

That does not make tax loss harvesting bad. It makes it a tool that should be used with a plan.

Let’s use your TSLA example to show the trade off clearly. These numbers are simplified to illustrate the mechanics. Your actual rates and outcomes depend on your tax bracket, state taxes, and whether NIIT applies.

Scenario A: You did not tax loss harvest

• You bought $10,000 of TSLA in November 2021.
• By March 2024, it is worth $5,000. You have a $5,000 unrealized loss.
• You do nothing. No sale. No harvested loss.
• By 2026, the position grows to $20,000. You sell.
• Your taxable gain is $10,000. If it is long-term, you pay long-term capital gains tax on the $10,000 gain.

Scenario B: You did tax loss harvest, then re-entered after 31 days

• You bought $10,000 of TSLA in November 2021.
• By March 2024, it is worth $5,000. You sell and realize a $5,000 loss.
• You wait 31 days, then buy back TSLA at roughly the same price.
• Your new cost basis is now based on the repurchase price, which is lower.
• By 2026, the position grows to $20,000. You sell.
• Your taxable gain is larger because your cost basis is lower, so you may owe more long-term capital gains tax on the TSLA sale.

• Scenario A, tax impact later: lower capital gains later (higher cost basis). No harvested loss to use now.
• Scenario B, tax impact now: you generated a realized loss that may offset gains and potentially a limited amount of ordinary income. The trade off is potentially higher taxable gains later because your new cost basis is lower.
• What decides which is better: what you offset with the loss today, what your future tax rates may be, whether NIIT applies, how long you hold, and whether you were going to keep TSLA regardless.

That is the point. Tax loss harvesting is not magic. It is a trade across time.

If you use the loss to offset high-rate income this year, it may be a big win. If you create a future gain that will be taxed at lower rates later, it may still be a win. If you harvest without a reinvestment plan and accidentally break your portfolio allocation, it can become a mistake.

Capital gains planning matters more when you have one or more of these realities:

• Liquidity events: IPOs, acquisitions, tender offers, and large one-time sales can create capital gains that dominate your tax year.
• Concentrated positions: tech professionals often invest where they are familiar, and familiarity can create unintentional concentration.
• Equity compensation: RSUs and stock options can create taxable income and capital gains in the same year, which increases the value of multi-year planning.

If equity compensation is part of your wealth engine, make sure your capital gains strategy connects to your equity strategy. This overview is a helpful bridge: Stock Option Taxes: How to Keep More of What You Earn.

For most high earners, the goal is not “pay the least tax this year.” The goal is to maximize after-tax wealth across the next decade while keeping flexibility for the life you want.

• Harvesting losses without understanding the wash sale rule: you can accidentally disallow the loss if you buy the same or substantially identical investment too soon.
• Harvesting just because the market is down: a down market can create opportunities, but only if the harvesting aligns with your broader plan.
• Ignoring cost basis tracking: basis can change due to reinvested dividends and other events. A wrong basis can create wrong taxes.
• Accidental short-term gains: selling before the one-year mark can turn a gain into ordinary income rates, which can be expensive for high earners.
• Forgetting NIIT: for some households, the extra 3.8% changes the math on large gains.

1. 1.
   Inventory your unrealized gains and losses: know what is up, what is down, and what is short-term versus long-term.
2. 2.
   Confirm cost basis method: make sure your brokerage is tracking basis correctly and that you understand what basis method you are using where it is applicable.
3. 3.
   Run a “tax delta” check before selling: ask, “If I wait until this is long-term, what changes?”
4. 4.
   If harvesting, define the purpose: are you offsetting gains this year, building carryforwards, rebalancing a concentrated position, or all three?
5. 5.
   Avoid unforced wash sales: if you sell for a loss, be intentional about what you buy during the next 30 days.
6. 6.
   Connect the tax move to the portfolio job: your portfolio should still match your timeline and risk plan after the harvesting trades.

• Capital gains tax planning is driven mainly by cost basis and holding period.
• Short-term gains can be expensive for high earners because they are typically taxed at ordinary income rates.
• Long-term gains can be more favorable, but NIIT may apply depending on your income.
• Tax loss harvesting can reduce taxes now, but it can also increase future taxes by resetting cost basis lower.
• The best harvesting strategy is tied to a broader plan, not a market headline.

• What are Capital Gains?: Foundational definitions and context.
• Harvesting Tax Losses to Beat Capital Gains A deeper walkthrough of TLH strategy.
• A Comprehensive Guide to NIIT for High-Income Earners NIIT details for high earners with investment income.
• Down Market Tactics: A Modern Investor’s Guide to Tax Loss Harvesting How TLH can fit into down markets without breaking your plan.
• Stock Option Taxes: How to Keep More of What You Earn Helpful context when capital gains overlap with equity compensation years.

• IRS: Questions and Answers on the Net Investment Income Tax (NIIT)

If you are a high earner, capital gains planning is not a once-a-year tax filing activity. It is a year-round decision system that should connect your portfolio, your equity compensation, and your future goals.

If you want help building a clear, coordinated strategy across taxes and investing, schedule a complimentary Financial Analysis here: https://go.oncehub.com/FreeFinancialAnalysis.