Accrual accounting records revenue when earned and expenses when incurred, even if cash moves later. At month-end, look for work performed but not billed and services received but not yet paid. Accrued revenue creates a receivable. Accrued expenses create a payable. The adjusting entry does not normally involve cash because no new cash movement occurred.
Use the part of the work that belongs to the reporting period. A payroll spanning month-end may contain only a few days of current expense. Interest accrues with principal, rate and time. Do not confuse an accrual with a prepaid expense: a prepaid starts with payment before use, whereas an accrued expense starts with use before payment.