Ref. TrackingID#2303310010000933 regarding the parameter "Safety level of invoiced orders" on Accounts receivable parameters - Updates. When selecting "Locked", you are not able to delete invoiced lines. However, you are not able to create credit notes on invoiced sales orders either. Therefore, the suggestion is to expand the possible alternatives to select for this parameter. For example adding an alternative as "Lock invoiced lines only", with this alternative it will still be possible to create credit notes from invoiced sales orders. The alternative which is named as "Locked" today can be renamed to for example "Lock invoiced orders", which still means that it is not possible to delete invoiced lines or create credit notes.