To view registers from last academic year, go to; Reporting > Reports > Attendance (red tab) > Official Register
Change the date range you want to view registers for. You may also want to select to include former students.
Click "Choose" and this will show you all of the registration codes for each child for that date range.
Note: You can only search every 31 days in the start and end date, so would have to do a month by month report this way if you wanted the registers for the whole academic year.