How can I effectively manage manual sales in an online store?

[wnwhelp]

Shopify online store linked to quickbooks online.

What is the best way to create manual sale? Do not have brick/mortar store, running out of home. If I get a drop in paying cash. Which is best way to record sale/create receipt. In orders in shopify or create sales receipt and record in quickbooks. If done in quickbooks inventory I am guessing inventory would have to manually updated in shopify. Any advice is much appreciated.