I found a good explanation:

"Those filing separately must report adjusted gross income separately from the spouse. No income assigning is permitted.

Both spouses must declare their own employment income or income earned as an independent contractor.

You must report rent-generating property you own, property earning royalties, or dividend income that you receive. Unless there is an unequal percentage of ownership of any of the aforementioned items that are jointly owned by both spouses, you must equally split all rents, royalties, and dividend incomes between the two of you for tax purposes.

When married couples file separately, both may claim either the standard deduction or itemized deductions of their own."