Can any one point me to a rule regarding what needs to be on the back of a monthly statement? Does a rule exist?

For deposit accounts, see Reg. E section 1005.8(b). For credit cards or HELOCs, see Reg. Z section 1026.9(a).

Thank you.

Neither of those requirements specifically says the disclosures have to be on the back of the statement. In each case, there is a longer version of the disclosure, which is to be delivered to the consumer annually. Or, again in each case, there's a shorter version that is to be delivered on or with each periodic statement. You get to choose the annual or periodic notice.