I'm aware of how the Itemized Deduction credit is calculated.  There is an error in the way Line 1 of that schedule is calculated.  It should use the amount from the worksheet and it wasn't if the amount on line 15 was zero.  It was erroneously bringing over the amount from Schedule A and giving the tax client a credit for medical expenses that they weren't entitled to. Support has development working on a fix that will be included in a future release.  For now, I need to override the calculation and then turn off the error routine for EFILE so that I can file the return electronically.