You should create and maintain Labour Codes by going into Labour>Labour Codes.  In that screen you can enter a charge rate.  You can also have different Charge Rates for the Labour Code by linking it to a Rate Level.  A Customer record contains the Rate Level that is applicable.

 

To create Rate Levels go into Labour>Settings>Rate Levels.  You can now establish Charge Rates for each Rate Level by going into Labour>Labour Rates.

 

To define that the Customer uses this Rate Level go into the Customer screen (Sales>Customers) and click on the ‘Pricing and Invoicing’ tab