Every adjustable-rate mortgage (ARM) uses a financial rate index (such as SOFR index or the U.S. Treasury-Index [T-Bills]) to determine the loan rate. Lenders have no control over financial rate indexes. For example, the SOFR Index is currently published by the Federal Reserve Bank of New York. The rate you pay is set at each adjustment period by adding your margin (which remains the same from period to period) to the rate of the index. Bank of America ARM rates are determined using the SOFR index, which is a broad measure of the cost of borrowing cash overnight collateralized by U.S. Treasury securities. Even though the SOFR index adjusts frequently, Bank of America adjustable-rates mortgages only adjust every six months after the initial fixed-rate period expires. Note: Bank of America is not affiliated with the New York Fed. The New York Fed does not sanction, endorse, or recommend any products or services offered by Bank of America.