Corporate evidence work, mainly. A recent sale or restructuring means the ownership chain must be documented as it now stands, sometimes across several entities. Add the cost of building the successor's employment history and drafting a position description that reflects a transition rather than a steady state.
Expect the company side to be the larger line
In a settled group, corporate evidence is a filing-cabinet exercise. After a handover it can involve counsel reading agreements to determine whether the relationship still qualifies. Ask for that review to be scoped separately, because its outcome may change everything downstream.
Then price the individual's preparation. Where a transition is under commercial pressure, decide what the business will spend on urgent work before it becomes an emergency decision. Hypothetical example: a regional distribution business budgets a succession filing at the same cost as the predecessor's, and finds the corporate review alone exceeds it because a holding company was inserted during the handover.
A first review would have scoped that review separately and completed it first, since its outcome determines whether anything else is worth preparing. Ask for it as a defined piece of work with a written answer, and agree what the business will pay for urgent work before commercial pressure turns that into a decision taken in a single afternoon.