Let me help you ease your confusion, @Vacil.

Creating an income account that was discussed above is for QuickBooks Desktop users. As mentioned by my colleague GarlynGay, in QBO, you'll need to create a vendor credit so the system will allow you to apply it to the bill payments as a discount. I'm here to assist you with this.

First off, we'll need to create a vendor credit using the inventory item. Here's how:

1. Click the Plus (+) icon.
2. Select Vendor Credit.
3. Choose the vendor name.
4. Fill in the necessary information.
5. Click Save and close.

Once done, you can now apply the vendor credit to the bill as a discount.  Please refer to the screenshot below.

Also, I want to let you know when creating a vendor credit will automatically reduce the COGS. However, I still encourage seeking help with your accountant. He/she could guide you which option to take based on your recording practice and business needs.

In case you need tips and related articles in the future, visit our QuickBooks Community help website for reference: QBO Self-help.

If you have any other questions, feel free to comment below. We're always here to help you.