Different clients, different rates. Here's how to configure hourly rates per project so invoices calculate themselves correctly.
Not every client pays the same rate. A long-term retainer client might get 150/hr. A short-term project with tight deadlines might be 200/hr. If your time tracking tool only supports a single rate, you're doing math on every invoice.
Rates per project, not per person
The cleanest model is to set hourly rates at the project level. Everyone who logs time on Project A gets billed at Project A's rate. This is simpler than per-person rates and matches how most agency contracts work — the client agrees to a rate for the engagement, not for individual team members.
Effective date ranges
Rates change. A client signs a new contract with a higher rate starting next quarter. You need both rates to coexist: the old rate for time logged before the change, the new rate for time logged after.
Effective date ranges handle this cleanly. Each rate has a start date and an optional end date. When you generate an invoice for a time period, each time log is matched to the rate that was in effect on that date. No manual overrides needed.
This seems like a small detail until you're reconciling a quarter where the rate changed mid-month and you need both rates on the same invoice with the correct hours under each.