Generally QB won't create actual duplicate accounts, where duplicate means they have exactly the same account name. Nor will let you create two accounts with the same full name manually.
In the IIF file:
- You must use the account name in the IIF file, not the description or account number.
- When importing data for sub accounts you must use the entire account name like Parent:Sub
Did you do both of those things? If not then that's why you got new unwanted accounts after import.
