Creating a bill of materials with landed costs isn't available in QuickBooks Online and is only available in QuickBooks Desktop, dpic44. Instead, you can create a bundle and service item to meet your needs. I’d be happy to share the steps with you.

For the Bill of Materials, you can create a Bundle for the products or services you sell together as a single item. For the Landed Cost, you can create a Service item and add it as a second line item in your invoice.

Here's how:

1. Go to Sales then select Products and Services.
2. Select New, then choose Bundle. 
3. Enter a Name for the product or service and an SKU, if you track them. 
4. Fill out the rest of the field, then click Save and Close. 

Then, do the same process when setting up your Service item. For the detailed process, refer to this article: Set up and track your inventory in QuickBooks Online.

Once done, create an invoice and enter the products/services you've created. See screenshot for reference.

On the other hand, you can reach out to our Intuit Developer concerning the sandbox. They can offer applications for your client to test and respond to inquiries regarding integration.

Additionally, I'll be sharing these resources that will guide you in pulling up inventory reports and recording customer payments in QuickBooks:

• Use reports to see your sales and inventory status in QuickBooks Online
• Record invoice payments in QuickBooks Online

If you require additional support while creating your new items, please don't hesitate to click the REPLY button below. I'm here to help you with any questions or concerns you may have. Stay safe and take care!