Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE CMI_Cross_References (master_customer_id VARCHAR, source_system_code VARCHAR)
TABLE: CREATE TABLE Customer_Master_Index (cmi_details VARCHAR, master_customer_id VARCHAR)

### Question ###
what are the details of the cmi masters that have the cross reference code 'Tax'?

### Accurate SQL ###

SELECT T1.cmi_details FROM Customer_Master_Index AS T1 JOIN CMI_Cross_References AS T2 ON T1.master_customer_id = T2.master_customer_id WHERE T2.source_system_code = 'Tax'