Sales order by department

custom product tags i am thinking of tagging all bar,kitchen etc items to their respective departments

So like a higher level group code?
Yer, item/product tag is ideal for that, probably more so than department.
So none of these products are available in multiple departments?

I had a similar issue with that same report since i have many departments too.I created a new database and restored my backup to the new database and voila
it worked.i really dont know how its related but it worked for me.

I tried it also by installing an enterprise version of 2014 (sp1), i had to reactivate sambapos but it didnt work for me. May you be willing to share a step by step guide on how you did it for yours to work.

Hence why I use (TE=x) and (PA=x) expressions. But as I said I dont use departments but rather map different Menu to different terminals in ticket type settings

This way you have mor control on where it was issues and where it was settled