How to create your estimates in QuickBooks, email them to customers, and then convert them into invoices after you complete the work 

Start raising quotes on-the-go with the QuickBooks Mobile App.

How to Create and Send Statements in Quickbooks online

How To Receive Payments - Apply Payment in Quickbooks online
If you have more than 2 bank accounts (*or you have Petty Cash) make sure that you select the correct bank accounts (Or Select Petty Cash) details in which the deposit was paid into.

If you are not too sure what to do, BE FRUGAL, GROW SMART and HIRE A BOOKKEEPER.