Accounts payable is usually defined as a current liability: amounts owed to suppliers for goods and services received but not yet paid. That is correct and it is only half of what the term means in daily use. The other half is operational: accounts payable is the queue of work that has to be cleared before a month can be closed. The accounting definition describes the balance; the operational one describes the deadline. Teams that hold both in mind run calmer months, because they stop treating payables as bookkeeping that can wait and start treating it as the thing that determines when the close can start.
As a liability: what belongs in the balance
Everything received before the cut-off, whether or not the invoice has arrived, and nothing received after it. The arrival date of the paperwork is irrelevant to the accounting and is exactly what most processes are organised around, which is the source of the friction. On the worked example on this site, $48,000 current, $21,000 at thirty days, $9,500 at sixty and $4,200 beyond is $82,700 owed, 42% of it overdue, with days payable outstanding of 30.26.
As a deadline: what has to clear
Invoices approved, exceptions resolved, accruals estimated for what is owed and unbilled. None of that is accounting work in the narrow sense and all of it has to happen before the accounting work can.
Why confusing the two causes overruns
A team that thinks of payables as bookkeeping schedules it after the cut-off, which is precisely too late. A team that thinks of it as a deadline clears it before, and the close begins from a known position rather than an unknown one.
Questions people ask about accounts payable is
Is accounts payable an expense?
No. The expense is recognised when the goods or services are received; the payable is the liability that arises at the same moment and is extinguished when you pay.
Is accounts payable debit or credit?
A credit balance, being a liability, and it is reduced by a debit when paid. The mechanics matter less than the timing, which is where the judgement is.
Does accounts payable include payroll?
Usually not; wages owed are normally shown separately. How your business classifies specific liabilities is a question for your own accountants.