As a financial institution having only savings passbook accounts, under Reg E we can avoid the periodic statement requirements by only allowing preauthorized recurring transactions or internal transfers. Question: If we allow non-recurring transactions (i.e. one time deposit entries such as IRS refund or a similar transfer in from an outside source) does this trigger the period statement requirement? We currently allow recurring credits and the passbook will update with the date and amount when next presented in person.

From Reg. E:
(c) Exceptions to the periodic statement requirement for certain accounts--(1) Preauthorized transfers to accounts. For accounts that may be accessed only by preauthorized transfers to the account the following rules apply:
(i) Passbook accounts. For passbook accounts, the financial institution need not provide a periodic statement if the institution updates the passbook upon presentation or enters on a separate document the amount and date of each electronic fund transfer since the passbook was last presented.
(ii) Other accounts. For accounts other than passbook accounts, the financial institution must send a periodic statement at least quarterly.
(2) Intra-institutional transfers. For an electronic fund transfer initiated by the consumer between two accounts of the consumer in the same institution, documenting the transfer on a periodic statement for one of the two accounts satisfies the periodic statement requirement.
(3) Relationship between paragraphs (c)(1) and (c)(2) of this section. An account that is accessed by preauthorized transfers to the account described in paragraph (c)(1) of this section and by intra-institutional transfers described in paragraph (c)(2) of this section, but by no other type of electronic fund transfers, qualifies for the exceptions provided by paragraph (c)(1) of this section.