I see a lot of things like this in the classroom; students manage to make errors I had never seen in the work place. I will try to help:

“Then later, when we do billing, these timesheet entries are pulled into the invoice to be generated, and (when things go as […]

Resolution for 'billing process issue: 'Why are timesheet entries not unchecked in billing process?' available: Yes.

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

For more information about resolving issues related to billing process in Quickbooks/QBO or to get support for the issue 'Why are timesheet entries not unchecked in billing process?', click the link below: