How To Fix CNV_20800012 - New customer number &2 already exists in the system; see long text

CNV_20800012 - Overview

• Message type: E = Error

• Message class: CNV_20800 - Message class for CNV_20800

• Message number: 012

• Message text: New customer number &2 already exists in the system; see long text

What causes this issue?

Customer record &V1& is to be renamed to &V2&. Customer record &V2&
exists in the system, but is not entered as <ZK>old value</> in the
mapping table. This would lead to an
<DS:TX.CNV_MBT_IMPLICIT_MERGE>implicit merge</>. This is not allowed.

How to fix this error?

If you want to merge &V1& and &V2& to &V2&, enter &V2&, as <ZK>old
value</> and as <ZK>new value</> in the mapping table and set the
priority flag accordingly. You can set the priority flag either for &V1&
or for &V2& .
If you do not want to merge &V1& and &V2&, you can:
Enter a value that does not exist in the master data table for new
<ZK>value</>
Or
Include &V2& also as <ZK>old value</> in the mapping table and enter a
different value for <ZK>new value</>.

Error message extract from SAP system. Copyright SAP SE.

CNV_20800012 - Details

• The SAP error message CNV_20800012 indicates that a new customer number you are trying to create already exists in the system. This error typically arises during data migration or when attempting to create a new customer record in the SAP system.
  
  Cause:
  
  Duplicate Customer Number: The primary cause of this error is that the customer number you are trying to create is already in use by another customer in the system.
  Data Migration Issues: If you are migrating data from another system, there may be overlaps in customer numbers.
  Incorrect Data Entry: There may be a mistake in the data entry process, leading to attempts to create a customer with an existing number.
  
  
  Solution:
  
  
  Check Existing Customers: Before creating a new customer, check the existing customer records to see if the customer number is already in use. You can do this by using transaction codes like XD03 (Display Customer) or FD03 (Display Customer - Financial).
  
  
  Use a