The billing is performed by several processes that run one after another.
Each operation is separate from any other operation and can be run out of order. However, some operations rely on DB output from prior operations, in order to perform actual work.
The operation flow is as follows: Receive -> Process -> Customer (guiding) -> Rating -> Pricing -> Tax
Running the processor should be enough in case all the xDRs are rated correctly.
In case some product / customer change was done, or in cases of rebalancing, the calculators should be run as well.