You would each report one half if you each own a 50% interest in the account.
Whom ever is listed first on the Brokerage firms Form 1099 should send a nominee Form 1099 to the IRS and the other person, The IRS instructions for Forms 1099 include the following:
Nominee/middleman
returns. 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 Internal Revenue Service 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.
Nominee forms 1099 are a pain in the neck. For future years, to avoid them, get that account out of both of your names by dividing it up.
