A sub (abbreviation for subaccount) must be defined per project. Subs are added from the budget tab of the project screen. new-sub

Subs can be set up to receive allocations at either the sub level or the type level (in this case ‘type’ is referring to ‘Cost Types‘). sub-allocation

Subs are generally set up similarly throughout an organization, so the budget tab on the project setup screen will allow users to either select from a drop-down list or enter text when defining a sub.

Subs must have an associated cost type.