To do so in ArchiOffice/EngineerOffice:
1. Create job codes with different billing rates in the Projects > Details > Job Codes screen. For example, set one at $70 per hour and another at $100 per hour.
2. Make sure the Active box is checked for both.
3. On the Phases tab, associate each phase with the relevant job codes. Again make sure each phase is Active.
4. Record time against each phase and job code.
5. Create an invoice for the same.
You will see two different rates recorded for the same employee across two phases.