Selling Investments Before Year-End? Why Tax-Lot Selection Can Change the Tax Result

In Colorado Springs, fall has a way of putting year-end deadlines in plain sight. The aspens turn, the first colder mornings show up, and if you are thinking about selling investments before December 31, 2026, this is still the window to review the actual tax lots before the trade is placed. That step matters because a sale that looks like one gain or one loss on the surface can produce a very different tax result depending on which shares are treated as sold.

How can tax-lot selection affect the taxable gain when I sell investments?

Tax-lot selection affects taxable gain by determining which purchase cost and holding period are attached to the shares you sold. If you own the same stock or fund in multiple lots, selling 100 shares is not one tax story. It may be 100 shares from a high-basis lot, a low-basis lot, or a mix, and each choice changes the realized gain reported for 2026.

Here is a clearly hypothetical example for an individual in Colorado Springs reviewing a contemplated taxable sale before year-end:

Lot	Purchase Date	Shares	Cost per Share	Total Cost	Holding Period by Late 2026
Lot 1	02/10/2023	100	$40	$4,000	Long-term
Lot 2	08/15/2025	100	$58	$5,800	Long-term
Lot 3	07/20/2026	100	$72	$7,200	Short-term

Assume the investor is considering selling 100 shares on 11/30/2026 for $65 per share, for total proceeds of $6,500, before commissions or fees.

If the investor uses specific-share identification and properly identifies Lot 3, the tax result is a $700 short-term capital loss because $6,500 proceeds minus $7,200 basis equals negative $700.

If the broker's applicable default basis method is FIFO, first in, first out, the 100 shares sold would generally come first from Lot 1. That creates a $2,500 long-term capital gain because $6,500 proceeds minus $4,000 basis equals positive $2,500.

That is a $3,200 swing in realized result on the same 100-share sale, simply from which lot is treated as sold. This is the heart of tax lot selection for capital gains.

The Internal Revenue Service requires taxpayers to determine basis and holding period for securities sold. Brokers also report basis information for many covered securities, but the tax result still depends on which shares were actually sold under the rules and records in place.

Why does the holding period matter along with basis?

Holding period matters because a sale can be long-term for one lot and short-term for another, even inside the same investment position. Tax basis answers how much gain or loss you have. Holding period answers what kind of gain or loss it is.

In the example above, Lot 1 and Lot 2 are long-term by late 2026, while Lot 3 is short-term. That means a specific identification choice can change two things at once:

• the dollar amount of realized gain or loss
• whether the result is short-term or long-term

A lot-level review is especially important when you made purchases across 2023, 2025, and 2026, reinvested dividends, or added shares during market dips and recoveries. I like to remind people that the newest lot is often the most forgotten one, and sometimes it is the one that changes the tax math the most.

According to FINRA, investors should understand the cost basis method on file with their brokerage account and how to make changes or provide instructions before selling. That is practical guidance, not just paperwork. If the wrong lot is attached to the sale, correcting it later can be difficult or time-sensitive.

What if all the shares are in the same account?

Being in one account does not make them one tax lot. Each purchase date and price can create a separate lot, and dividend reinvestments may create many smaller lots over time.

That is why tax lot selection for capital gains is transaction-specific. The account may show one position with 300 shares, but for tax reporting purposes you may really own 3 lots, 12 lots, or 40 lots.

What basis records should you have before placing the sale?

You should have enough records to show acquisition date, share count, purchase cost, and any basis adjustments for the exact shares being sold. If those records are incomplete, a CPA can help compare your records to the broker's basis reporting before the transaction is completed.

Useful records often include:

• brokerage statements showing each purchase lot
• trade confirmations
• 1099-B forms from prior years
• records of dividend reinvestment purchases
• transfer records if shares moved from another broker
• documentation of stock splits, mergers, or inherited basis where relevant

The U.S. Securities and Exchange Commission notes that cost basis reporting and tax treatment can depend on account records and investor instructions. That becomes more important if shares were transferred between custodians, because transferred basis data is not always clean.

What if the broker's basis record looks incomplete?

If basis data looks incomplete, do not assume the tax result is fixed. Missing transferred lots, incorrect acquisition dates, or absent reinvestment records can all distort the gain shown in a sale preview.

This is one reason some Colorado Springs individuals ask us to review the transaction before they sell, through our tax services work. The goal is not to tell you whether to invest or sell. It is to help evaluate how the contemplated taxable sale may be reported.

How do broker identification procedures work for specific-share sales?

Specific-share identification usually requires timely instructions to the broker identifying the exact shares or lots to be sold. It is not enough to decide later, after the trade settles, that you meant to sell different shares.

Procedures vary by broker, but the process commonly looks like this:

1. Review the lot list for the security in the account.
2. Choose the exact lot or lots to be sold.
3. Provide those instructions through the broker's trading interface or representative before the sale is executed.
4. Keep written confirmation showing the identified lots.
5. Verify after the trade that the confirmation reflects the intended lots.

Weak version: "Sell 100 shares."

Stronger version: "Sell 100 shares of XYZ from the lot acquired 07/20/2026 at $72 per share."

That difference may sound small, but for tax lot selection for capital gains it is the difference between a generic trade order and a documented lot instruction.

What is the default method if I do nothing?

The default method depends on the asset type and account setup, but for many stock positions the default is FIFO unless another method has been established. You should confirm the method actually on file with your broker instead of guessing.

If mutual fund shares are involved, average basis rules may be relevant in some cases. That is exactly why a sale should be reviewed at the transaction level rather than treated as a single blended gain or loss.

When should a Colorado Springs taxpayer ask a CPA to review the sale?

The best time to ask is before the sale is placed, while there is still time to compare lots, basis records, and broker procedures. Once the trade is done, your options may narrow quickly.

A pre-sale review may be worth it if any of these apply:

• you bought the investment in multiple lots over 2, 3, or more years
• some shares are long-term and others are short-term
• the account was transferred between brokers
• you reinvested dividends over time
• the contemplated sale is large enough that a basis error would be meaningful
• you want plain-language help understanding what the broker is likely to report

If you are already doing other year-end tax review, this can fit naturally into that conversation. For some readers, our article on Roth IRA income limits is a helpful companion on another investment-related tax issue, but this article is narrower on purpose. We are talking about one specific pre-sale tax question, not a broad year-end checklist.

You can also get a broader sense of firm capabilities at pattersontaxcpa.com. I think tax planning works better when the scope is clear. For this issue, the scope is the sale in front of you, the lots behind it, and the records that support the reporting.