I want to know how you bill per phase? Which phase you will bill the most normally? If various by contract pay amount, which fee system? ie. Lump Sum, Cost Plus Fix Fee, GMP ( Guarantee maximum).
This is a Project management question, Billing per phase is typically done through the project Breakdown structure (WBS) which takes the client budgets and divided among the five or six design phase after you account for your consultant fees which usually in the range of 30% to 40% of the architect’s fee. Then take that amount and divides it into Predesign 5% SD 20% DD 25% CD 35% Bidding 5% CA 10%, once you Breakdown the Architect fee into phases, then you can further break it down per design staff. Breaking it down per staff is basically taking each phase budget and divide that by the firm billing rate, which get you the maximum hours you can spend per phase and then you assign staff members appropriately based on their utilization and billing rate.
Your questions about contract fees are directly correlated with the project delivery method, each delivery method has a fee structure that is best suited for that project type. I would suggest reading chapters 7 & 9 of the Architects professional practice handbook. Hope this helps.