Can I change a "Customer" to a "Vendor"?

Thanks for posting your concern here in the Community, dttinsley15.

I'll ensure you can customer to vendor in QuickBooks Online.

Currently, we don't have a direct way to do this. As a workaround, you can make the customer as inactive and recreate them again as a vendor.

Before proceeding, consider editing the customer's name first before we delete them because QBO doesn't allow duplicate names. Then, follow the steps below when you're ready to make them inactive. I'll show you how:

1. Go to the Sales menu at the left pane, then Customers.
2. Click the Customer's name to open their information.
3. Go to the Customer Details tab, then click Edit and Save.
4. Edit the name, then click  Save.
5. Go to the drop-down beside Edit and click Make inactive, then tick Save once done.

Once done, recreate them again as a vendor using the customer's information. Here's how:

1. Got the Expenses tab at the left pane, then Vendors.
2. Click New vendor, then enter the necessary information.
3. Hit Save.

For additional information about managing your customers and vendors in QBO, you read through these articles: 

• How to edit customer information.
• Vendors overview.

Additionally, you’ll want to pull up some reports that can give you a snapshot of your business by visiting this article: Run reports in QuickBooks Online

I'm more than willing to listen if you have any other concerns with your QBO transactions. I'll ensure your needs are taken care of.