So you don't need to bend over backwards and deal with months of IRS letters ... may I suggest you just put all the income on the one return whose SS# it was reported on then divide the extra tax by half and have the other spouse reimburse that person or withhold it from the division. This will save you grief from IRS hassles later down the road.
To easily do this just complete the return without the common income and note the bottom line then add the common income and note the new bottom line. Then divide the difference in half and settle up with the other person.
