First, a couple of observations which are not relevant to your question about syntax, but do affect how you express this thought:
- When we are talking about the work we do from an external viewpoint, as something done for clients and customers, we usually speak of services. (From an internal viewpoint, we speak of work, a non-count noun, rather than works, which are what is produced by artists!)
- Similarly, we tend to use expenses to refer to internal costs, what we as a company have to pay out; externally, when we pass those costs/expenses through to the client, we speak of charges. It's particularly
So your original sentence would look like this:
Travel costs were also incurred as [when] the services were provided, in whose charges they were included.
This is grammatically acceptable; but as J.R. has told you, it's always good to tighten up the relationships so the sentence is easier to parse. In this case your most important thought is that certain costs were passed through to the client, so make that your main clause, and subordinate the clause which explains which costs were passed through. (In this example the piece in brackets may be omitted; it's just there to make the structure more evident.):
Travel costs [which were] incurred in the course of providing services were passed through to client charges.