Report what you relied on. If it's negative, it's negative. Old HMDA generally held that gross income can't be negative, but new HMDA say's it's ok.
"Finally, the Bureau notes that the 2015 HMDA Final Rule and the 2018 FIG do not include any language that would bar a financial institution from reporting an applicant's gross annual income as “0†or even a negative number when that is the accurate figure that it relied on."