Form 8615 line 9 uses the Schedule D tax calculation worksheet to calculate the combined family tax using the parent's filing status. When you are under the $89,250 limit lines 44 and 45 do not fill in properly with 0's.  They just stay blank. I can not override it if I want to file electronically. It then calculates a large tax liability. If you are over limit at 89,251 it works as expected and automatically fills in the tax amount at a much lower amount.  The difference is $6000 dollars plus on the child's return that I am preparing.