Hi there, @dannyt3. I'll provide information about this below.
To begin with, the option to delete a payment in QuickBooks Online (QBO) is unavailable due to transaction history purposes. However, you can set the payment method to inactive. Here’s how to do it:
Navigate to the upper right corner and click on the Gear icon or Settings.
Under the Lists section, select All Lists.
Choose Payment Methods and click the dropdown icon next to the payment method you wish to make inactive.