Creating a city code in SAP – or modifying existing one – is pretty simple in the customization transaction.
Starting from SPRO, the customization transaction, go to Sales and Distribution > Basic Functions > Taxes > Define Regional Codes
There, select Define city code
Click on New Entries
The Country key will have to be selected first
Additional information can then be entered : Region, City code, Description
A Customizing request will be prompted for
The creation of the new city code will be notified – and that’s it !