You are trying to change or edit the Bank Account ID which is already assigned in the bank master data.
Reproducing the Issue
- Go to Liquidity Management work center.
- Go to My Banks View.
- Select the My Bank ID XYZ.
- Edit -> Bank Accounts.
Here you see Bank Account id is grayed out. You are not seeing any option to edit.
In SAP Business ByDesign system, bank account is considered master data, so once it's created, it cannot be deleted or either changed.
The bank account ID is unique key that cannot be changed once it's saved, either from frontend or backend.
System behavior is as designed.
In case you want to have a different Bank Account ID for this bank account, you can edit the bank account, and in the Bank Accounts tab of the bank master data, select the bank account item and choose Actions-> Close this Bank Account, and create a new bank account with the correct bank account ID.
KBA , SRD-FIN-CLM , Cash and Liquity Managment , How To