When I export from QB Desktop to QB Online, an old, zero-balance account in Desktop that has been marked as "inactive" for some time now suddenly becomes active again when it reaches QB Online. But when I try to make it inactive, QB Online pops up an error saying: This account cannot be inactivated because there are transactions in it that have a non-zero balance (see attached).
Can anyone tell me exactly what that means and how to fix it?
And in case it's relevant, this is a foreign currency account. (However its final balance is ZERO, in both the foreign currency, and when converted to my home currency which is USD.)
 It's not exactly clear. I mean, of course transactions have non-zero balances; that's just what a transaction is surely?
It might have been reactivated when you converted your QuickBooks Desktop file to QuickBooks Online. If this is an Accounts Receivable or Accounts Payable account, we recommend merging each account in the Chart of Accounts into one.
There are certain default and special accounts that you cannot inactivate. Check this article for more information: How to manage default and special accounts in the Chart of Accounts.
Should you need any further assistance, please don't hesitate to leave a comment below.