The following cites are from the August 2023 FIG.
Enter, in dollars, rounded to the nearest thousand, the gross annual income relied on in making
the credit decision, or if a credit decision was not made, the gross annual income relied on in
processing the application (round $500 up to the next $1,000). The HMDA Platform can accept
negative numbers for Income.
Appears $0 income was the amount used in making the credit decision.
(2-80) Paragraph 4(a)(23)—Debt-to-Income Ratio.
Enter, as a percentage, the ratio of the applicant’s or borrower’s total monthly debt to the total
monthly income relied on in making the credit decision. Use decimal places only if the ratio
relied upon uses decimal places. The HMDA Platform can accept up to 15 decimal places and
can accept negative numbers for Debt-to-Income Ratio.
In this case the applicant's debt divided by $0 would equal 0%.
I don't recall seeing any guidance that prohibits reporting 0 as the DTI.
The opinions expressed are mine and they are not to be taken as legal advice.