What is the term for costs that have been incurred but not yet paid?

Costs that have been incurred but not yet paid are called accrued expenses.

An accrued expense arises when a business has received goods or services, or employees have earned compensation, but cash payment has not happened yet. Under accrual accounting, the expense is recognized when it is incurred rather than when money leaves the bank. The unpaid amount is recorded as a liability, often under accrued liabilities or trade and other payables.

For example, employees may work during the final week of December but receive their wages in January. The company records the December payroll expense and a corresponding liability, then reverses or settles that liability when payment is made. Similar examples include interest, utilities, rent, and professional services received before billing.

Accrued expenses differ from prepaid expenses, which are paid before the related benefit is received and begin as assets. Deferred revenue is cash collected before the company earns revenue, so it is also a liability but not an expense. A contingent liability depends on a future uncertain event, whereas an accrued expense is generally much more certain in timing and amount.