There are exactly three rates in StaffVertex. Nearly every invoicing question is really a question about which one applied.
1. The client bill rate, on the project
What the client pays per hour for work on that project. It lives on the project's finance section and produces the billable invoice.
There is no per-member version of this. A client is quoted one rate for the project, not a different one depending on who happened to do the work.
Fixed-price projects have no bill rate at all, because the client agreed a price instead of a rate.
2. Pay per hour, on the project
What members earn for working on that project. Also on the project, and easy to confuse with the bill rate. The difference is direction: bill rate is money in, pay per hour is money out.
It applies to fixed-price projects as well, because people are paid by the hour whatever the client agreed.
3. The member's own pay rate, on the person
An individual rate on the member's profile, for someone paid the same wherever they work. Set it when you invite them, or later on their profile.
Which wins
The member's own rate beats the project's pay per hour, resolved for every single day. The project rate is the baseline for everyone, and an individual rate is the exception for one person.
Neither of them ever affects the client bill rate. What you pay and what you charge are independent.
Rates have effective dates
Each of the three is a history, a list of rates with the date each took effect, and not a single number. The rate applied to a given day is the latest one effective on or before that day.
This is what makes a mid-period raise work correctly: hours before the change are priced at the old rate, hours after at the new, all on the same invoice.
Setting them before work starts
Enter rates when you create the project and when you invite the member. Adding a rate after hours are tracked means re-pricing invoices that already exist, which works but is more to check.
If no rate can be found
Hours with no rate in force cannot be priced. Those lines are flagged and the invoice is held in draft instead of sent short.