Not a problem, neither in a principles-based jurisdiction nor in the US under Sarbanes Oxley. Need to keep reminding management that both preparation of fin stats AND tax computations are their responsibilities. Ideally, different people prepare tax comps, different from audit staff.
Must ensure that total fee from that client or group of clients does not exceed 15% / 10% rule
As usual, independence, objectivity and competence are relevant as is the concept of confidentiality