Query for linking tables

[Guest_imported]

I am trying to create a query involving 4 tables. I need to join fields from 2 of the tables and get a sum for the 2 fields. These fields have the same heading but are for different years. We design a report that shows totals for paid invoices and some are from 2000 and some from 2001 - but 2000 and 2001 are in different tables. So somehow the query needs to join these 2 sales tables - the 3rd table is a dealer list which is linked by customer # and the 4th is a tax table. But if I can figure out how to join certain fields in these 2 tables, I think I will be ok. Any suggestions?
faith

 

[Guest_imported]

I suggest using a union query to combine the 2 tables into one then subquery from there