The general rule is that a depositor may make no more than six covered transfers or withdrawals per calendar month or statement cycle.

Can the bank use a calendar month for certain accounts and the statement cycle for others? Or must we use the same period for all accounts?

You can use --
* calendar month, or
* statement cycle of at least four weeks, or
* similar period of at least four week.

There is no prohibition on using more than one of those options across your account portfolio. For example, you might have business savings or MMDA accounts that all cycle at month end and personal savings or MMDA accounts that cycle on other days of the month, but each cycle is a month long. You can monitor the count based on either the statement cycle or the calendar month. Customers generally find it easier to work with statement cycles, I think.

If you have quarterly savings cycles for some accounts, don't use the statement cycle itself. Instead use a monthly period or one-third of the statement cycle. It just has to be at least 4 weeks long.