Don't get me wrong. There are many benefits to using QuickBooks Online over Desktop. But getting your financial set-up properly may not be as easy as Intuit would like you to believe.
This is especially relevant for those looking to upload past financials into QuickBooks Online. QBO automatically downloads 90 days of bank info and gives you the option of importing the rest. But it is difficult to manipulate and the process is very error prone.
A much simpler solution is to use QuickBooks Desktop and to reconcile all your financials before getting started with QuickBooks Online. Once ready, Intuit makes it very simple to upload your desktop data to the online version.
The online version is notoriously bad at matching downloaded transactions to existing ones, so the worst thing you can do is just arbitrarily add new transactions to QuickBooks, as Intuit makes it very easy to do. Instead, try and manually enter as many transactions as you can from within QuickBooks, such as writing checks and paying bills.
Consistency of how you add transactions and regular maintenance are key to keeping the system working.