The standard Profit and Loss structure includes 2 headings for income; 'Income' & 'Income - Other'. These are considered to be categories that relate to the ordinary operations of the business. If there are any "non-operating" income accounts (eg Interest Received), you can allocate them to "Other Income" which appears at the bottom of the Profit and Loss report. You can add additional income categories under Chart of Accounts. 

In the example below, the income categories have been added to track "Income from Labour" v "Income from Non-Labour" (eg Parts etc);

Note that the standard "Income" & "Income-Other categories" will still appear, however they will only show on the reports if a value exists.

If you have multiple entities or divisions, it may be useful to establish Divisions so you can segment your projections and view the reports on either a divisional or consolidated basis. 

Once the Division has been established, they will appear as a filter option in the Profit and Loss Projection as shown below;

Ensure that the accounts have been assigned to the Division under Chart of Accounts and you can then proceed to enter the projections at the Divisional level. The sum of the Divisions will report at the "All Divisions" level. 

No it is not compulsory to use Income Drivers. Income Drivers can be used if you want more detailed projections. For example, you may want to project the income based on # Products x average $/Product or # Hours x Avge $/hour x % Utilisation. 

The What-if Analysis will show the Income Driver breakdown which will allow you to consider what-if scenario's in more detail.

If you are not using Income Drivers, you can simply enter the value in the relevant month and Copy Across the value to future months if required (by double clicking on the value). 

If you want to project the income as a % of another account there are 2 options;