Per Regulation DD – Truth-in-Savings, if a checking account has a tiered-rate feature (different rates apply to specified balance levels), if new balance levels are added to the account product (not a money market) are we required to send a notice to existing account holders? The new balance levels will be above the existing balance levels, so this change would be in the customers favor.
Even though you state it will be a beneficial change to the customer, I would recommend providing 30 days advance notice for changing the tier structure. While you might not be cited for not providing the notice 30 days in advance, I think you could avoid potential questioning by an examiner (who thinks you should have) if you go ahead and do the advance notice.