Accounting
Liability
A liability is an outstanding payment obligation: a mortgage, personal loan, consumer credit, card balance or debt owed to someone else.
A liability is valued at its outstanding principal, not the sum of future instalments: those instalments include interest that hasn't accrued yet, which would artificially inflate the debt.
In double-entry bookkeeping, each loan instalment splits into principal repayment (reduces the liability) and interest (an expense for the period).