Don't sub accounts have the same account number as the primary account?
Not usually.
Each bank account has a specific role.
The account would have the bank branch number and then an account number to ID usage.
Say a customer had an account with sub accounts & wanted a deposit to go to sub-account #1, the deposit would need correct 'numbers' or go to the wrong account. (More work/costs for a bank & unhappy customer)
Just to let you know i have done a lot of work and not getting very far so thats why i asked on here. I thought we joined to help each other, which i have done in the past but maybe some people think that has all changed.