NACHA Guidelines for Federal Deposits

If an ACH federal deposit is presented, in the past we used the payment to cover the charged off account. Now, we have been told that NACHA rules state we must return all deposits on closed accounts and can no longer offset the closed/over drawn account. One of our concerns is we are in a community with a large military base, with a large volume of military accounts with a federal deposit, which is the customers' Army pay. And as you can imagine, we also have a large volume of accounts that charge off. I was told that under NACHA guidelines we're now suppose to return all federal deposits. Can you help me define what is included under federal deposits?