I looked into this for our students with dietary requirements. There was a lot of 'pointing fingers' going on between us, our canteen provider, our payment software, Sims and NRS. The main (but not only) problem seemed to revolve around the fact that we're running an older version of the Trust-e software, that has limited functionality in this area.
It got too hard so we resorted to supplying the kitchen staff with a list of students where care is required. Hardly ideal but it works for us as we are a small high school and the kitchen staff know our students.