Entering credit card credits through QuickBooks Online App is unavailable. You can use the app to add notes, photos and attachments to transactions.
I’d suggest, that you enter the transactions using a web browser.
You can read this article for more information: Compare mobile app features.
Resolution for 'QuickBooks Online app issue: 'How do you enter a credit card refund in the Mobile app?' available: Yes.
The QuickBooks Online app 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 QuickBooks Online app issue yourself by looking for a resolution described in the article. If it is a complex QuickBooks Online app issue or you are unable to solve the issue, you may contact us by clicking here or by using other QuickBooks Online app support options.
For more information about resolving issues related to QuickBooks Online app in Quickbooks/QBO or to get support for the issue 'How do you enter a credit card refund in the Mobile app?', click the link below: