This business would have nobody owing them money, it's retail and they would owe suppliers as they bought stock in, income is just from daily sales. There is nothing else to 'attach' to in this case either I imagine.
I didn't actually read the document initially, but having had a quick skim now, I see that it is written in a way that assumes a certain amount of knowledge on the part of the reader (who is intended to be a revenue case worker).
I think this is why you're still missing the fundamental point here - the bank is a "debtor" of its customer - it owes them whatever balance of money is in their account. Where an attachment order is issued to a bank in respect of a specific account, any positive balance will have to be handed across to Revenue (subject to any right to off-set that the bank may have, as explained in page 10 of the TDM).
So, if money continues to be lodged to the account (e.g. in the case of a retailer this may include most of their turnover unless they don't accept card payments) then the bank will be required to keep handing that money straight across to Revenue.
In effect, this means there'll be no money in the account for paying anyone or anything else, until the sum specified in the attachment order has been discharged.
Words like blocked and frozen are inaccurate for describing what's happening in the case of an attachment - it's more like Revenue having hijacked the account so that all money flowing into it goes to them, meaning there's none available for withdrawing, or honouring direct debits / standing orders / cheques...