The 4 letters for the code are generally on the second page of the EIN letter.

Lacerte may populate with what they believe is correct but there is no consistency despite e-filing a return with no issues for several years

I said earlier it appears that the first 4 letters of the first part of the trust name generally but not always works as I just did one earlier this week where the first 4 letters of the third word in trust name worked

It is difficult to get through to the e-file help desk too