I just figured out that this must be a bug, and now I see from this forum that it should be a known bug, since it is not new. At least I won't waste anymore time trying to get TT to do the calculation correctly. Certainly reduces my trust in the software. My plan is to lie to TT and enter it all in one 1098, then keep a manual worksheet with the correct calculations with my records, just in case. That way, TT will give me the correct deduction. If you don't already know this, IRS Pub 936 describes the various ways to calculate this. The IRS never sees the worksheets, it just matches the deduction against the 1098(s) that it received.
