Hi there, Summer. Thank you for joining this thread. To narrow down your concern, I can provide information on what to do if your inventory is lacking.

It's possible to send an invoice to your customer even if your inventory is negative. However, we can prevent negative inventory by creating a purchase order for the item. This will help replenish your list and ensure you can ship the item by the pre-order date.

Here's how :

1. Go to Vendors, then select Create Purchase Orders.
2. Select Create Purchase Order.
3. Fill out the fields, then select Save.

Once done, you can visit and follow these articles for you to have detailed steps:

• Receive an inventory with a bill.
• Pay the Bills from the Purchase order.

In addition, you can also send an estimate to your customer if you want to let them know first, and without having your inventory deducted: Create an estimate in QuickBooks Desktop

Also, you can check this article  to learn how to adjust the quantity or total value of your products in QuickBooks Desktop: Adjust your inventory quantity or value in QuickBooks Desktop

Don't hesitate to leave a comment if you have more concerns about managing your inventory, or any other Quickbooks-related issues. I'm always here to help you. Take care.