Accounts payable is a liability, not an expense. It represents an amount owed to a supplier. The related purchase may be recorded as an expense or as an asset, such as inventory or equipment, depending on the transaction and applicable accounting rules.
Under accrual accounting, paying the supplier is not what determines when an expense is recognized. For example, a current-period service received on credit may create an expense and a payable when recognized. Later payment reduces cash and the payable; it does not create the same expense a second time. An asset purchase follows the relevant asset-recognition and expense-allocation rules.
For background, see the SEC’s AP definition and FASB’s explanation of accrual accounting. Your finance team determines the treatment of individual transactions.