Capital Gains Taxes: Basis, Sales, and Reporting
In brief
A taxable investment sale generally creates a capital gain or loss equal to the amount realized minus adjusted basis, but holding period, netting, and reporting rules determine the federal tax treatment.
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The main idea
Track basis and holding period before selling; the account statement alone may not capture every adjustment or every transaction that affects the return.
At a glance
Core calculation
Proceeds − basis
The difference is generally the gain or loss before applicable adjustments and special rules.
Internal Revenue Service ↗Reporting path
Form 8949 + Schedule D
Most capital transactions are reported and then summarized through these forms.
Internal Revenue Service ↗Account scope
Taxable accounts
Publication 550 says its investment-income rules do not govern assets held inside IRAs and qualified plans.
Internal Revenue Service ↗Basis is the starting record
Adjusted basis usually begins with acquisition cost and can change because of reinvested distributions, return-of-capital payments, certain corporate actions, and other adjustments. Selling price by itself is not taxable gain.
Reinvested dividends purchase additional shares. They may be taxable when paid in a taxable account and also become basis in the newly acquired shares, so accurate lot records matter when those shares are sold.
Netting and filing are separate from the headline rate
Federal reporting separates short-term and long-term transactions before netting gains and losses. Special categories, state taxes, the net investment income tax, and other return items can change the result.
This guide explains mechanics rather than calculating a tax bill. Use the current tax-year forms and instructions, and seek qualified tax help when basis, inherited property, business interests, options, or multiple jurisdictions are involved.
Before acting
Questions to verify
- Confirm the account is taxable.
- Verify adjusted basis for each lot.
- Identify acquisition and sale dates.
- Reconcile Forms 1099-B and 8949.
- Check current federal and state rules before filing.
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