Edit Page Error - Cannot update identity column

Hi Everyone,

I have an order form that I use the identity column as the Order Number. When I add that field to my Edit page, as READONLY because I don't want to update it just display it, and try to save my record I get the error shown in the figure below. I don't want to update the identity column value, just display it on the edit form. Not sure what I'm missing but if anyone can point me in the right direction I would greatly appreciate it.