What is "bank account UNN"? This question is about iTunes Connect, particularly Agreements, Tax, and Banking section. When I open this section I see the red message:


  Our records indicate that your banking information is incomplete. Please access your banking information and update as necessary.


Screen:


So, following this recommendation I go to Bank Info > Edit > View/Edit Existing Bank Account > Edit Bank Account Info

There I see a new field which wasn't there when I first entered the banking information. It's named UNN. Quick help:


  Enter the nine-digit UNN for your account.


Screen:


So the question is, what is the UNN associated with a bank account? 

I've called to my bank and they didn't know anything. Also, I've already asked this question on Apple forums, but there was no response for a week.
The UNN code is a Taxpayer’s code (INN, UNN or UNP code (natural persons don't have codes UNN or INN) needed for payment transactions in/to Belarus. (Source)