There’s an interesting discussion in WooCommerce Issue #2571. regarding the default state of the “Deliver to a different address” checkbox.
For a less cluttered checkout screen and from a UX view point, we could uncheck it by default
Add this code to your functions.php
add_filter( 'woocommerce_ship_to_different_address_checked', '__return_false' );
Or to enable it by default add this code to your functions.php
add_filter( 'woocommerce_ship_to_different_address_checked', '__return_true' );