Neither Reg C nor the HMDA Guide give this as a reason for using N/A for the rate spread. Here are the reasons to us N/A according to Appendix A in Reg C
(https://www.ffiec.gov/hmda/pdf/2013guide.pdf):
b. If the loan is not subject to Regulation Z, or is a home improvement loan that is not dwelling-secured, or is a loan that you purchased, enter “NA.”
c. Enter “NA” in the case of an application that does not result in a loan origination.
and
e. If the difference between the APR and the average prime offer rate is less than 1.5 percentage points for a first-lien loan and less than 3.5 percentage points for a subordinate-lien loan, enter “NA.”
Here’s a link to information on an Rate Spread of NA from the HMDA Rate Spread calculator: https://www.ffiec.gov/ratespread/oldcalchelp.aspx. Scroll down to “Rate Spread Equal to NA”.