There are two main business accounting methods: cash and accrual. Cash accounting is the simpler method because it’s based on the actual flow of cash in and out of a business. The cash method is used primarily by sole proprietors and businesses with no inventory. On the flip side, accrual accounting records income and expenses as they occur, whether cash has actually changed hands or not.
As they grow and become more complex, most small businesses should switch to accrual accounting, because this makes it easier to accurately match revenue to expenses. Otherwise, the business might look profitable during months with few expenses and unprofitable during months with large expenses, with no way of really knowing the difference.