você deve acessar o arquivo form-shipping.php que se encontra em wp-content/plugins/woocommerce/templates/checkout
no arquivo form-shipping.php procure pela linha
<input id=”ship-to-different-address-checkbox” class=”input-checkbox” <?php checked( $ship_to_different_address, 1 ); ?> type=”checkbox” name=”ship_to_different_address” value=”1″ />
e substitua por
<input id=”ship-to-different-address-checkbox” class=”input-checkbox” <?php //checked( $ship_to_different_address, 1 ); ?> type=”checkbox” name=”ship_to_different_address” value=”1″ />
e pronto.