If a partnership reports other than tax basis capital accounts to its partners on Schedule K-1 in Item L (that is, GAAP, 704(b) book, or other), and tax basis capital, if reported on any partner's Schedule K-1 at the beginning or end of the tax year would be negative, the partnership must report on line 20 of Schedule K-1, using code AH, such partner's beginning and ending shares of tax basis capital. This is in addition to the required reporting in Item L of Schedule K-1.
I have not been doing this. I understand why they want this, of course.
Did anyone else know this was in the instructions?