Cost basis matters because it directly impacts how your clients’ stock transactions are evaluated, taxed, and ultimately reported to the IRS. Understanding what cost basis in stocks are helps determine whether a sale results in a gain or a loss, which is key information for accurate tax filing and compliance.
For tax preparers, cost basis is not always straightforward. It can change based on how the asset was acquired and what adjustments occurred over time. In this article, we break down how cost basis works across common scenarios you will encounter, including stock purchases, gifted shares, inherited investments, and property transfers due to divorce, so you can confidently guide clients and report transactions correctly.
What is cost basis?
Essentially, a cost basis describes your client’s total investment in a particular asset. Cost basis begins with the original cost or value of an asset and adjusts it for factors such as stock splits, dividends and returns of capital distributions. After these changes are applied, the updated value is often referred to as the adjusted cost basis.
Cost basis can be viewed in two ways. It may represent the total investment in a position, or it can be broken down into a cost basis per share, which is especially useful when clients buy and sell portions of the same investment at different times. Ultimately, cost basis is an indicator of whether an investment results in gains or losses, which is what your client will need to report for tax purposes.
How to determine cost basis for stock
The cost basis of your client’s stock depends largely on how it was acquired. Common scenarios include stock purchases, gifts, inherited assets, and transfers as part of a divorce. Each situation has its own rules for establishing the starting basis, which is why it’s important to identify how the investment entered your client’s portfolio.
It’s also important to note that cost basis is not always fixed. Additional factors over time can affect the final basis used for tax reporting. For example, adjustments such as stock splits, dividend reinvestments, returns of capital distributions, and certain fees or commissions can all change the original amount.
Stock purchases
For stock purchases, cost basis starts with the paid per share and includes any commission or fees your client paid to complete the transaction.
For example, if your client buys 10 shares of ABC Company stock at $20 per share:
- $20 x 10 shares = $200 (initial investment)
- $200 + $100 (commission paid to a broker) = $300 (total cost basis)
- $300 /10 shares = $30 (cost basis per share)
Now, assume your client sells those 10 shares for $50 each and pays $100 in commission on the sale.
- $50 x 10 shares = $500 (gross proceeds)
- $500 – $100 (commission paid to a broker) = $400 (net proceeds)
- $400 – $300 (original cost basis) = $100 gain
In this example, the sale of the stock ultimately resulted in $100 in gains.
Gifts
The cost basis for gifted stock depends on whether the asset is ultimately sold as a gain or a loss, so it cannot be determined until the stock is sold.
- If it’s sold at a gain (appreciated asset), your client uses the original owner’s cost basis. This is often referred to as a carryover basis, meaning the donor’s basis transfers to the recipient.
- If it sells for a loss (depreciated asset), your client uses the lower of the original owner’s cost basis or the fair market value of the stock at the time of the gift.
Inheritance
Inherited stock is subject to a special tax provision known as the step-up in basis. The rule adjusts the cost basis of the asset to its fair market value on the date of the original owner’s death, rather than the price they actually paid for it.
As a result, your client’s starting basis is typically the asset value at the time they inherit it. This can significantly reduce the amount of taxable gain, especially if the stock appreciated during the owner’s lifetime.
Your client, as the recipient of the inheritance, is only responsible for paying taxes on the appreciated value after they took possession of the asset.H3: Divorce
- Add that in a divorce, property transfers between spouses are generally non-taxable, but the recipient retains the original cost basis (carryover basis)
- Add that unlike inheritance, there is no step-up in basis to current fair market value during a divorce, meaning the client may inherit significant hidden tax liabilities
Divorce
In a divorce, property transfers between spouses are generally non-taxable. However, the receiving spouse takes on a carryover basis, meaning they inherit the original owner’s cost basis in the asset.
Unlike inherited assets, there is not step-up basis to reflect the current fair market value at the time of transfer. This distinction is important because it means the recipient may also inherit significant built-in gains or “hidden” tax liabilities tied to the asset.
As a result, when the asset is eventually sold, the receiving spouse is responsible for any taxes on appreciation that occurred both before and after the transfer.
Cost basis methods for tax reporting
How cost basis is calculated at the time of sale can vary depending on the method your client uses, and that choice directly impacts how gains or losses are reported. When multiple shares are purchased at different prices over time, selecting the right method becomes especially important for accurate tax outcomes.
Some of the most common cost basis methods include:
- First In, First Out (FIFO): This default method assumes the first shares purchased are the first ones sold. In a rising market, FIFO can often result in larger taxable gains because older shares typically have a lower cost basis.
- Specific identification: This method allows your client to select exactly which shares are being sold. By choosing shares with a higher cost basis, clients may be able to reduce their taxable gains or increase reported losses.
Each method can produce different tax results, so it’s important to understand how they apply and ensure consistency in reporting.
Where Does 1099-DIV Box 3 Non-Dividend Distributions Show On the Form 1040?
Non-dividend distributions do not need to be reported anywhere on your client’s tax return because they are treated as a “return of capital” and are not taxable in most cases.
Instead, the amount in Box 3 should be used to reduce your client’s cost basis in the investment. This adjustment is important for accurately calculating future gains or losses when the asset is sold.
Over time, repeated non-dividend distributions can significantly reduce the basis. In an edge case where these distributions reduce the cost basis to zero, any additional non-dividend distributions must be reported as capital gains in the year they are received.
