Married Filing Separately, how do I split dividend from joint investment accounts between me and my spouse?

The easiest way is to just split them 50/50, if both names are on the 1099-DIV. If only one name is listed, that party can indicate Nominee income for the other party.

(See the attached screenshot below. Click to enlarge.)

The rules can be different (and complicated) if you live in a community property state (Arizona, California, Idaho, Louisiana, Nevada, New Mexico, Texas, Washington, or Wisconsin ) and have to allocate income.

I can't see a screenshot but have same question.  Do we just each put 50% of each item (box information) from the 1099-DIV document?

That will work whether you are in a community property state or not.

@TerriAron