Earlier quoted context omitted.
> There is no "legal paperwork" for accounts. ...so I can just throw away all the tax documentation for my mid/high tier interest bearing checking and savings accounts at both my credit union and bank? that share certificate I have at my credit union generating dividends? "Legal" to me means "things I have to do or the police come find me." Your interpretation might be different, but my accounts have legal paperwork.
Is that "legal paperwork" something which you (the end user) has to do, and not something that the credit union/bank does?
Both parties submit paperwork to the IRS - the institution tracks the assets they're holding/managing and reports it to the IRS on their side; they issue you appropriate documents and you do your taxes and report it using whatever appropriate form. The paperwork is of course dependent on the situation, for the average checking/savings accounts I will guess it's the 1099-DIV as most common - simple interest payments.