"Under Art IBB of Allen ...Family Trust" is the way its in the SS-4 I learned yesterday.  The code on page 2 is "UNDE".  I picked up the trust from another CPA and he had it in the return as "Allen....Family Tr" and Proseries autopopulated the code to ALLE.  It worked for 6 years.  Now I will try to change it to UNDE except ProSeries software appears to not allow it w/o an error code.