After some digging to make the payment reference as mandatory for journals without using "Method of payment", I didn't face any solution to cover this requirement.

So whenever a user remove the method of payment, or making a normal bank transfer, there won't be any control on that, and he isn't obligated to enter the transaction payment reference.

However, I then encountered a localized functionality for Iceland called "Set up mandatory payment references", it requires the payment reference to be mandatory per main account, which is an okay solution, so this functionality should not be localized, Or at least a new functionality should be introduced to cover this part either by making it mandatory on the Journal Name level, or making the method of payment mandatory on the journal name, and this would make more control somehow, to always obligate the user to choose the appropriate method of payment, but I also believe that the both would be there for more control.

• Mandatory payment reference on the journal name
• Mandatory method of payment on the journal name.