BLACKROCK ALLOCATION TARGET SHARES BATS: Series M Portfolio BATS: Series S Portfolio BLACKROCK BALANCED
CAPITAL FUND, INC. BLACKROCK BOND FUND, INC. BlackRock Total Return Fund BLACKROCK FUNDS^SM BlackRock Managed Volatility Portfolio BLACKROCK FUNDS II BlackRock Core Bond Portfolio BlackRock GNMA Portfolio BlackRock Investment Grade Bond Portfolio BlackRock Low Duration Bond Portfolio BlackRock Multi-Asset Income Portfolio BlackRock Strategic Income Opportunities Portfolio BlackRock U.S. Government Bond Portfolio BLACKROCK FUNDS III BlackRock Bond Index Fund BlackRock CoreAlpha Bond Fund BLACKROCK GLOBAL
ALLOCATION FUND, INC. BLACKROCK SERIES FUND, INC. BlackRock Balanced Capital Portfolio BlackRock Global Allocation Portfolio BlackRock Total Return Portfolio BlackRock U.S. Government Bond Portfolio BLACKROCK VARIABLE SERIES FUNDS, INC. BlackRock Global Allocation V.I. Fund BlackRock Managed Volatility V.I. Fund BlackRock Total Return V.I. Fund BlackRock U.S. Government Bond V.I. Fund MANAGED ACCOUNT SERIES BlackRock U.S. Mortgage Portfolio

(each, a “Fund” and collectively, the “Funds”)

Supplement dated January 10, 2014 to the
Statement of Additional Information of each Fund

Effective immediately, the following changes are made to each Fund’s Statement of Additional Information:

The section captioned “Investment Risks and Considerations — When Issued Securities, Delayed Delivery Securities and Forward Commitments” is amended to add the following:

Pursuant to recommendations of the Treasury Market Practices Group, which is sponsored by the Federal Reserve Bank of New York, beginning January 1, 2014, a Fund or its counterparty generally will be required to post collateral when entering into certain forward-settling transactions, including without limitation TBA transactions.

Shareholders should retain this Supplement for future reference.