On my 3115, I have an adjustment on line 19 because
I held a stock into the year that I elected M-t-M.
This amount is less than 25k so I don't need to put it
over 4 years. Where on the 1040 does this number transfer
I can't find anywhere that this number applies.
I am working from memory, but I think this will get you to the right answer on your 1040.
It seems to me that 3115 has a section that flows to the 4797 where your other trading gains are reported. Now from there I had one trader respond that he put the income from 4797 on Line 21 of the 1040. This works as the net calculation of tax would be correct.
Now if you can't find a logical place on 4797 to report your MTM gain(just for the stock held), you could drop it on Schedule D Part 1. And I would just include a note to the IRS of where you did the calculation. This would then roll as a short term gain, after the netting on the back of the form is done. The result from a net tax standpoint is the same.