Options to populate Tax Book

Hello,

We are looking to migrate assets from an acquisition that have a separate tax book in their current system.  In their current system they have retired many assets from their Corporate book which remain in their tax book.  What are the options, for our migration to Oracle, to get the information related to those historically retired assets populated into the Tax book?  As I understand it, an asset has to exist in the Corporate Book before it can exist in the Tax book so I'm not certain of the correct process to populate the tax book with the correct information.