I am trying to define the Retained Earnings Account using "X" for P & L statement type and giving the GL account number that I propose to use for the Retained Earnings Account.
The account is not getting created. The system is not accepting "X" or any other alphabet.

I have checked my Chart of Accounts creation step by step but cannot find anything wrong.
Will be grateful for any help. It is on S/4 HANA 2021.