Veeqo will allow you to accept pre-orders from Shopify for products that you currently have no physical stock for in your location. That means your real stock of 0 is set correctly in Veeqo, but the item will still be available for purchase on your Shopify.
Your pre-orders will come into Veeqo as "Waiting For Stock" and therefore sit separately from your "Ready To Ship" orders, to avoid any confusion.
Important: Veeqo must be Master of Inventory for the above process to work. If Veeqo is not Master of Stock then all orders will be assumed Ready to Ship
How to enable pre-orders on Shopify?
1. Log into your Shopify Admin;
2. Go to Products>Inventory;
3. Find the product you want to accept pre-orders for and scroll to the inventory section;
4. Set a checkmark for the options "Track quantity" and "Continue selling when out of stock"
5. Click Save.
Orders for these pre-order products will go into Waiting For Stock and once you receive stock Veeqo will automatically assign stock based on oldest order first until all available stock is allocated.
Shopify has a great guide that makes it clear on your store that this product is on a backorder basis.