Yes, the closing date is the start date for the integration. However, due diligence should include a number of things required for integration planning, even if the PMI team is not directly interfacing with the target team that will be performing the work. For example, key systems, KPIs and employees to retain should all be included in DD summary reports. This can be incorporated into the general integration plan for system migration and employee journey, with the understanding that the high level plan will ultimately be honed once there can be a more open discussion post-closing. I would argue that that high-level integration plan should be shared back to the target company during the acquisition process, so that expectations are clear on the ultimate goals on both sides of the deal.
