How does JIRA determine what Fields to show when Moving an Issue?

[Tim]

I have two projects (A and B) and cannot figure out what fields show up when moving an issue. 

Some constraints:

• Both projects have a lot of unique custom fields (meaning that some custom fields only belong to A and some only belong to B, and some overlap)
• Only 1 or 2 fields are required for issue creation

When I try to move from project A to B, I am given the option to update A LOT of fields, not all of them are required, and the order htey show up in is random. For example, the Assignee field is at the bottom. In all our screens, the assignee field is at the top of the page. But, when I move an issue from B to A, I only see one field. 

What determines this? Any ideas for what I can check?

[Nic Brough -Adaptavist-]

It shows you all fields it needs any information on because they do not exist in the source setup.  The order is not that random - it lists all the built-in "system" fields in a fixed order (from memory, I can't remember if that's alphabetic, but it's the same all the time), then custom fields alphabetically.

[Tim]

But, in my situation above, going from B to A lists only 1 field whereas A to B lists many. I can't make sense of it.

[JamesV]

It is my understanding that you will be prompted for any field that is not in the originating issue type screen.