woocommerce_vat_countries filter-hook . WC 1.0

Usage

add_filter( 'woocommerce_vat_countries', 'filter_function_name_1514' );
function filter_function_name_1514( $array_merge ){
	// filter...

	return $array_merge;
}

$array_merge

-

Where the hook is called

return apply_filters( 'woocommerce_vat_countries', array_merge( $eu_countries, $vat_countries ) );

Where in WP core the hook is used WooCommerce