Task
This field can only be entered on a financial document detail line item if the Account entered on that line item has been identified as a project related account (that is, if the Account was configured on the Admin >> Setup >> Accounts screen with the Require Project indicator checked).
The tasks available will be limited to:
Only those tasks having an Owning Organization (should one be specified) that belongs to the same Legal Entity as the Legal Entity specified on the Financial Document.
Additionally, a Task value is required if the previous restrictions are met and the project is configured to require a task for expense reporting (as defined on the Project Profile).