If there is an agreement between you how the income is to be reported during the joint period you can use the amounts agreed upon. If not, then 50/50 would be the correct way to handle it.
The financial institutions would typically use one social security number to report the earnings each year on joint accounts. The person whose number is used can "nominee" the correct portion to the other spouse by using the instructions below.
Nominee returns. Generally, if you receive a Form 1099 for amounts that actually belong to another person or entity, you are considered a nominee recipient. You must file a Form 1099 with the IRS (the same type of Form 1099 you received). You must also furnish a Form 1099 to each of the other owners. File the new Form 1099 with Form 1096 (this is a transmittal for the 1099) by mailing to 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 nominee filer, not the original payer. The nominee is responsible for filing the subsequent Forms 1099 to show the amount allocable to each owner.
The forms filed with the IRS should be the red copy so if you don't have a color printer, go to the IRS website and order the forms here: Click here to order forms or publications from the IRS.
The income will be reported based on the type such as interest, dividends, capital gains, etc.