The item you use on an invoice (or any transaction) determines what account is posted to.  So from the sounds of it, you need a service item posting to income-regular (selected as the income account on the item screen), and another service item posting to income-assessment – and then use […]

Resolution for 'appropriate service issue: 'Using multiple Income Accounts?' available: Yes.

The appropriate service 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 appropriate service issue yourself by looking for a resolution described in the article. If it is a complex appropriate service issue or you are unable to solve the issue, you may contact us by clicking here or by using other appropriate service support options.

For more information about resolving issues related to appropriate service in Quickbooks/QBO or to get support for the issue 'Using multiple Income Accounts?', click the link below: