You probably use the cash method. The most common method is CASH. It means you report your income in the year you actually receive it and report your expenses in the year you actually pay them. See,
https://ttlc.intuit.com/community/business/help/what-is-the-cash-method-of-accounting/00/25658
The ACCRUAL method of accounting is often used by businesses that carry an inventory. You report your income in the year you earn it (not when you receive it) and report the expenses in the year you incur them (even if they aren't paid yet). See,
https://ttlc.intuit.com/community/business/help/what-is-the-accrual-method-of-accounting/00/26034
