Debt is when you owe money to someone.
Yes, or it could be a moral debt as well couldn't it?
Debt
Debt is when something, usually money, is owed by one party, the borrower or debtor, to a second party, the lender or creditor. Debt is a deferred payment, or series of payments, that is owed in the future, which is what differentiates it from an immediate purchase. The debt may be owed by sovereign state or country, local government, company, or an individual. Commercial debt is generally subject to contractual terms regarding the amount and timing of repayments of principal and interest. Loans
which a moral fact supervenes could be quite complex, with many exceptions and qualifications; for instance, one might only be obliged to pay someone $10 if the recipient has not waived the debt, or does not intend to use the funds to cause immediate harm to someone else, etc.
As the principle of moral supervenience by itself places no limit on what the non-moral supervenience base of any moral fact is, nor on how complex the former might be, it is generally considered a very weak principle.