How do I report capital gains on my 1040 Schedule D when I share a joint brokerage account with my sibling and my SSN is used by the brokerage.

[KrisD15]

The proper way is for you to issue a 1099 to your sister for her share. 

Next, you enter the 1099 from the Brokerage and make an adjustment for the amount that belongs to your sister. 

This is known as being a "Nominee".

Here are the steps to make that nominee adjustment

Wages & Income

Investment Income

Stocks, Cryptocurrency, Mutual Funds, Bonds, Other START 

Select "Stocks, Bonds, Mutual Funds"

Continue

Skip Import

Complete the "Which bank or brokerage is on your 1099-B?" screen and continue

Click through the questions if necessary to get to the screen-

NOW CHOOSE HOW TO ENTER YOUR SALES

Be sure to select "Sales section totals" and Continue

On the "Now, enter one sales total on this 1099-B"  screen -

Enter the Sales section (type of Capital Gain), Proceeds and Cost 

CHECK THE BOX FOR "I need to adjust my total cost basis" 

A drop-down list appears with adjustment codes

Scroll down and Select N (nominee for actual owner of property) 

Enter the amount of the gain as a negative number or the amount of the loss as a positive number

Continue

The following screen should show 0 gain/Loss 

You will need to mail a copy of the 1099-B with Form 8453 with or without your return (the 1040 return may be e-filed).

Here are instruction on mailing Form 8453 with your 1099-B

According to the IRS:

"Generally, if you receive a Form 1099 for amounts that actually belong to another person, you are considered a nominee recipient. You must file a Form 1099 with the IRS (the same type of Form 1099 you received) for each of the other owners showing the amounts allocable to each. You must also furnish a Form 1099 to each of the other owners. File the new Form 1099 with Form 1096 with the IRS Submission Processing Center for your area. On each new Form 1099, list yourself as the “payer” and the other owner as the “recipient.” On Form 1096, list yourself as the “Filer.” A spouse is not required to file a nominee return to show amounts owned by the other spouse. The nominee, not the original payer, is responsible for filing the subsequent Forms 1099 to show the amount allocable to each owner."

https://www.irs.gov/instructions/i1099gi#:~:text=Generally%2C%20if%20you%20receive%20a,the%20amounts....

[Golong]

Thanks.

This is helpful.  I didn't realize that I would have to do the 1099 entries manually. Thanks for that guidance.  I will work through the 1099 filing issue as I am past the deadline for those.