Cash vs Accrual Method
There are two main ways to prepare a Schedule C: using the accrual method or the cash method. Under the accrual method, you report income when it's earned, even if you haven't yet received payment. Under the cash method, you report income when you receive payment.
Most small businesses use the cash method, because it's simpler and easier to track. However, there are some exceptions, so be sure to check with your accountant to see which method is best for your business.