[Selling Stock] Can I change my cost-basis retroactively?

[jatron]

Suppose I own two shares of company XXXX, one acquired for $3,000 in January 2020, and one acquired for $9,000 in July 2020. In December 2020 I sell one share of XXXX for $6,000. In February 2021 I receive a 1099-B from my broker with the transaction recorded as follows:

1a-Description of property: 1 sh. XXXX

1b-Date acquired: January 2020

1c-Date sold: December 2020

1d-Proceeds: $6,000

1e-Cost basis: $3,000

Realized Gain or (Loss): $3,000

Can I change my cost-basis retroactively to elect to sell the share acquired for $9,000 in July 2020? This would allow me to offset ordinary income with net capital losses of $3,000 (instead of reporting a $3,000 short-term capital gain).

(Note: I understand that I can change my cost-basis election with my broker, but this would only apply to future transactions. The question here is if I can change the cost-basis after I've made the trade.)

[JohnB5677 · Accepted solution]

No, the standard rule for transactions is First In First Out (FIFO), unless as you said you declare something different before you do the transaction.

The 1099-B is correct.

If you had planned ahead you could have sold both lots and had zero gain.  End of the year planning is very important.