Debt to service coverage ratio in fixed income

Debt to service ratio takes (debt over interest) or ( debt over interest+ principal repayment)?

Net operating Income / (Principal repayment + Interest payments)

at the very first page of FRA book there is a formula list, take your time.

Debt Service Coverage Ratio (DSCR) = First Year Net Operating Income (NOI) / Debt Serivce

If the financing is an amortizor, you would include the scheduled principal payment in addition to the interest payment.

DSCR = NOI / Debt Service = (Annual Net Income + Amortization/Depreciation + Interest Expense + other non-cash and discretionary items (such as non-contractual management bonuses)) / (Principal Repayment + Interest payments + Lease payments)