Ubercart

+1 for this suggestion if nothing has already been implemented (I haven't been able to find anything much) although it looks as if it has been discussed here previously.

The idea suggested that the prefix is created as a seperate field looks ideal for what I need (need to be able to quickly identify where payments have came from [multiple web shops paying into the same bank account] in order to keep the books up to date). Has any work been done on this at all?

I also need this. Let's continue this discussion here.

Also I have uploaded a contrib module that does not solve the problem completely, but may be useful depending on your needs:
Order Number Prefix

small problem regards order number:
see that is an auto_increment value, every user can know which is the number of orders that the shop's owner have managed;
infact every user have in the list of own order the Order # ;
and also this isn't useful for user to have a number of orders that really is of the shop's owner;

possible solutions:
1-
in the view user not see the field of order but a field that number only the rows;
at click can always open the order (so in the url remain always total order of shop but is less evident )

2-
to have in the table uc_order in addition at fields
order_id
uid

a field uid_no (uid relative number order)

where is insert the number of order
example
order_id uid uid_no
10 2 1
11 2 2
12 2 3
13 3 1
14 4 1
15 2 4

tha for every user set the numbers of order;

so shop's owner can have in own view other at order_id, also the other two fields and with possibility of make order
not only on order_id but also with uid;