Confirm the current ownership chain first, because a failure there ends the analysis. Then reconstruct the employment history across the closing date, then compare the duties before and after. Only once those three are settled does a filing timetable mean anything.
Let the dependencies set the dates
Each step feeds the next: the structure determines which entity issues the supporting letter, and the service history determines which reference period the qualifying year sits in. Integration projects add delays of their own when signatories change roles mid-way. Set milestones for the ownership confirmation, the payroll retrieval, and the duty statement, then discuss travel.
Avoid promising a start date to the receiving team while any of the three remains open. Add one further dependency that acquisitions reliably produce: the people who can explain the transaction are the busiest people in the organisation and are frequently leaving. Deal counsel move on, integration leads are seconded elsewhere, and the finance manager who understands why an entity was renumbered often departs once the integration completes.
Ask at the outset who those people are and take what is needed from them first. Hypothetical example: a footwear brand's integration finance lead, the only person able to explain a change in payroll numbering across the closing date, has a notice period ending in six weeks, and the chronology survives only because that conversation was moved to the front of the schedule rather than left in its natural position.