You could also add account numbers as a custom field under Settings.
Let me also make a couple points. First, @lubos has mentioned plans to move towards having more and more information be in custom fields. Customer codes are left over from early days of the program. I don’t know exactly how he will plan for data migration, but you might want to use a custom field from the beginning to avoid potentially having to re-enter anything later. Second, do not expect the program to autonumber a scheme like yours. After all, who could predict blending abbreviations for customer occupations with numbers, and if someone did, how could all possible combinations be predicted? Some people like easy-to-remember codes with a few letters. Others like detailed account numbers that encode service locations and levels, etc. So if you get an autonumber capability in Manager, it will most likely be the same as the one for sales invoices: find the highest existing number and add 1.