Prenote transaction code does not populate in ACF

The NACHA transaction code field is not being populated in ACH files.  I went to add  mapping for prenotes in code mapping, but I don't know what the input value is for prenotes.  So what I did was to check the Return Input If No Match Is Found.  My understanding of that is that if a code for prenote is not found, it will populate the ACH file with whatever I have in the input field.  In this case it was 22.  However, that still did  not work.  Is there a Peoplesoft code for prenote?  If not, then how how