If your savings or secondary checking account does not have enough available funds to cover the necessary amount, we may decline to make the transfer. (bankofamerica.com)
When the Overdraft Protection transfer is made from a linked deposit account (U.S. Bank consumer savings account, money market or a secondary checking account), there is no fee. (usbank.com)
You link your primary external checking account to your savings account to perform transfers, and can also link a secondary checking account. (lendedu.com)