QB Issue Resolution:

I think they missed this one. The way I see it, there is no way assign class (or setup class) for discount. You can assign GL account, but not class. It just goes to “Not Specified” class. I guess you can write a journal entry to reclassify to appropriate class.

If you feel this feature need to be added in future revision, please add your voice here.

http://feedback.qbo.intuit.com

Resolution for Issue 'How can I assign a class to “Discount Percent” on Invoices in QuickBooks Online?' available: Yes (Solved).
Source: Intuit Community forum.

How can I assign a class to “Discount Percent” on Invoices in QuickBooks Online?: this issue or error code is a known issue in Quickbooks Online (QBO) and/or Quickbooks. Support for this issue is available either by self-service or paid support options. Experts are available to resolve your Quickbooks issue to ensure minimal downtime and continue running your business. First try to resolve the issue yourself by looking for a resolution described below. If it is a complex issue or you are unable to solve the issue, you may contact us by clicking here or by using other support options.

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