Opening balance
The starting amount in each account in the statement of financial position at the beginning of the reporting period.

Opening statement of financial position
The statement of financial position at the start of an entity or the date of transition to IFRS.

Operating activity
The principal revenue-producing activities of the entity involving producing and delivering goods or providing services and other activities that are not classified as financing or investing activities.

Operating assets
Assets  necessary to operate a business, including current assets and plant assets used in operations, and excluding non-operating assets such as land held for future use or idle plant assets.

Operating expense
An expense incurred in the normal course of running a business, but not directly associated with production. Operating expenses include sales commissions, transportation, office payroll and office rent. Also called nonmanufacturing expenses, these expenses are often divided separately into selling expenses and administrative expenses.

Operating profit or loss
The total of operating revenues less operating expenses, excluding all financial and other non-operating income and expenses as well as the components of other comprehensive income. Also called operating income or operating result

Opportunity cost
An term in economics that means that the next best alternative that has been foregone. This may represent the time taken or money lost from not choosing a particular option.

OS&E
Operating supplies and equipment.

Outturn cost
The agreed final construction cost of a development project.