You either have to issue a credit memo to the customer for the item or you have to set the customer up as a vendor & enter a bill or a check.
Resolution for 'add a purchase issue: 'how to add a purchase from a customer' available: Yes.
The add a purchase 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 add a purchase issue yourself by looking for a resolution described in the article. If it is a complex add a purchase issue or you are unable to solve the issue, you may contact us by clicking here or by using other add a purchase support options.
For more information about resolving issues related to add a purchase in Quickbooks/QBO or to get support for the issue 'how to add a purchase from a customer', click the link below: