My company currently only has one customer as we sub-contract all our work to them and they do the direct-to-customer sales. But we are about to change that and start selling services and products directly to customers. 

We currently do all of our bookkeeping in Quickbooks Online, and with no inventory to keep up with, it's pretty simple. Once we start selling, we will be doing both online and in-person sales, with at least the online sales being through (most likely) Shopify on our website. 

How do I bring the online sales into Quickbooks online without looking like I've duplicated sales? Or is there a way to bring in the numbers without the transactions so I can still do accurate reporting?

And what about the inventory? If I sell online and in-store, how would I keep my inventory synchronized across both systems?