Re: Issue with filters in case of multiple data files.
If you need to use selections in IOU and other fields then merely make sure that the names of the fields that should be used to link the three tables have the same names in all three tables. A synthetic key will be created to link the tables so perhaps you'll want to replace the synthetic key with a new key to a link table that will have all the original values from the common fields of the three tables. See this blog post: Concatenate vs Link Table
Concatenating tables can be done in the Data Manager or in the Data Editor.