You’ve run a Profit and Loss statement, but the revenue seems way too high for what you know your sales have been. The first place you should look is in your Undeposited Funds account. If this account has a growing balance, then you have not been following a proper workflow in QuickBooks, and have probably duplicated some deposits.
Customer payments that are received through Undeposited Funds must then be deposited through the Bank Deposit window in QuickBooks. This will allow the income transaction to be matched when it flows in through the bank feed. If the payment has not been deposited in this manner, then the bank feed won’t match the transaction for you. Since you don’t see a match, you may record the income again, effectively doubling that income in your books.
Always be sure to follow the proper workflows so that QuickBooks will work seamlessly for you!