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The Daily Insight

How do you determine the basis of a stock sale?

Author

Emma Jordan

Published Mar 28, 2026

You can calculate your cost basis per share in two ways: Take the original investment amount ($10,000) and divide it by the new number of shares you hold (2,000 shares) to arrive at the new per-share cost basis ($10,000/2,000 = $5).

What is adjusted cost basis stock?

Cost basis is the original value of an asset for tax purposes, usually the purchase price, adjusted for stock splits, dividends, and return of capital distributions. This value is used to determine the capital gain, which is equal to the difference between the asset’s cost basis and the current market value.

What’s the cost basis for selling a stock?

The Internal Revenue Service (IRS) says if you can identify the shares that have been sold, their cost basis can be used. 1  For example, if you sell the original 1,000 shares, your cost basis is $10.

What do I need to use to show the adjustment?

What code do I need to use to show the adjustment of cost basis to 1099-B for employee stock sales? When entering sales of employee stock purchase plan stock, Turbo Tax mentions that the Box A (or D) 1099-B cost basis provided by the financial institution is incorrect and the supplemental information they provide has the correct cost basis.

How are basis adjustments calculated for a corporation?

Basis adjustments are normally calculated at the end of the corporation’s taxable year. First, they are increased by income items; then decreased by distributions; and, finally, decreased by deduction and loss items.

Is it possible to put stock basis back together?

Unless the tax accountant preparing the shareholder or company tax returns has the foresight to begin and maintain the basis calculations, piecing stock basis back together is like reconstructing a mosaic without all the pieces—it’s tedious, often difficult and sometimes nearly impossible.