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 customer_master_index ( master_customer_id number, cmi_details text )
TABLE: CREATE TABLE business_rates ( business_rates_id number, cmi_cross_ref_id number )
TABLE: CREATE TABLE parking_fines ( council_tax_id number, cmi_cross_ref_id number )
TABLE: CREATE TABLE electoral_register ( electoral_register_id number, cmi_cross_ref_id number )
TABLE: CREATE TABLE rent_arrears ( council_tax_id number, cmi_cross_ref_id number )
TABLE: CREATE TABLE cmi_cross_references ( cmi_cross_ref_id number, master_customer_id number, source_system_code text )
TABLE: CREATE TABLE benefits_overpayments ( council_tax_id number, cmi_cross_ref_id number )
TABLE: CREATE TABLE council_tax ( council_tax_id number, cmi_cross_ref_id number )

### Question ###
Which cmi cross reference id is not related to any parking taxes?

### Accurate SQL ###

SELECT cmi_cross_ref_id FROM cmi_cross_references EXCEPT SELECT cmi_cross_ref_id FROM parking_fines