Lightspeed OnSite allows you to connect directly to certain accounting softwares. Alternately, you can export your accounting information to import into compatible programs.
Lightspeed Retail can export your accounting information for importing into QuickBooks Desktop, however Lightspeed Accounting offers up many more options and automates much of the process for you.
Unfortunately, there is little overlap between the accounting softwares that work with OnSite and those that work with Retail.
If you've been handling your accounting completely manually, you can continue to do so with Lightspeed Retail. Otherwise, we'd recommend investing in Lightspeed Accounting and a compatible accounting software. Lightspeed Accounting offers many advantages, most notably the fact that once it is set up, your sales, payments, discounts, taxes, etc will all sync over to your desired accounting software automatically every morning, saving you a great deal of work. You also have more control over how that information is organized in your accounting software.
If you prefer, you can manually export your accounting information and import it into QuickBooks Desktop using the export options built in to Lightspeed Retail.