Every business has "sales." Most call this "revenue." QB calls this "income." All is money from customers.
Some companies sell products and many only sell services. Services are hours worked = labor dollars.
You are right that the sum of money coming IN on bank statement is the total amount of Cash you received.
This should match the total Debits (increases) to your Cash account (account is oddly called "Bank" in QB).
This is made up of one or more of the following:
1) Revenue from customers (QB calls it "Income"). This is normally first account or accounts on P&L.
2) Other Income (Usually a separate account or accounts at the bottom of P&L) that may include:
2a) Interest Income (Such as earned on investments or bank account).
2b) Refunds from vendors (Such as for returned items or overpayments).
2c) Refunds from tax agencies (Such as for overpayments made in error).
2d) Proceeds from Sale of Fixed Assets (May be a gain or loss).
It is important to split these amounts between category 1 and 2.
#1 - Should have customer invoices on AR Aging pending customer payment receipt
#2 - Would not have customer invoices and may need to be moved to another account
If you see duplicate amounts for customer invoices, you may have posted duplicate invoice or payment.
If you are creating fake invoices, you could be doubling invoice amounts and/or posting duplicate payments.
In my P&L I also see invoices that have been paid when I run it on a cash basis. We don't have sales so I usually just psudo invoice, pay the invoice and most of the time when I run a P&L it's showing the income on my bank statements (that's how I check the income). However, when I run last years P&L several invoices are showing in there with a duplicate amount as the deposit. I deleted those without any problem or un-reconciling my months but there are invoices showing in there that are actually mistakes but no way to delete these without screwing up my reconciliation for the year. This is crazy, how do I get them out of my P&L because they are showing income and they were never received....running cash basis only.