Asset, Liability, and Equity type accounts have perpetual balances. Balances for Income and Expense type accounts are theoretically reset to zero at the end of each accounting period, with the difference posted to the Equity account. QuickBooks uses nested accounts, which can be up to up to 5 levels deep. The balance of any nested account is automatically summed to it's parent. Accounts Payable, Credit Card, Other Current Liability, Long Term Liability.
Accounts can optionally use account numbers.
There is an option in the file preferences to require account numbers when an account is entered, but most of the time it is not used. Does not include colon separators or names of parent accounts. If account numbers are not being used, there is no guarantee that each account will have a number. Any numbers that exist are returned, even if not used - however there is no enforced scheme for user entered numbers. In the QB IIF documentation, this is mistakenly listed as the opening balance of the account - it is actually the current balance.