Customizing Checkout Field Order http://wordimpress.com/15-woocommerce-code-snippets-im-thankful-for/ Sometimes the default ordering of fields isn’t optimal for your business. You can modify the order the fields appear by customizing the following function:

wc-reorder-fields.php

<?php
  add_filter( 'woocommerce_checkout_fields', 'reorder_woo_fields' );
  
  function reorder_woo_fields( $fields ) {
  	//move these around in the order you'd like
  	$fields2['billing']['billing_first_name'] = $fields['billing']['billing_first_name'];
  	$fields2['billing']['billing_last_name']  = $fields['billing']['billing_last_name'];
  	$fields2['billing']['billing_company']    = $fields['billing']['billing_company'];
  	$fields2['billing']['billing_address_1']  = $fields['billing']['billing_address_1'];
  	$fields2['billing']['billing_address_2']  = $fields['billing']['billing_address_2'];
  	$fields2['billing']['billing_city']       = $fields['billing']['billing_city'];
  	$fields2['billing']['billing_postcode']   = $fields['billing']['billing_postcode'];
  	$fields2['billing']['billing_state']      = $fields['billing']['billing_state'];
  	$fields2['billing']['billing_country']    = $fields['billing']['billing_country'];
  	$fields2['billing']['billing_email']      = $fields['billing']['billing_email'];
  	$fields2['billing']['billing_phone']      = $fields['billing']['billing_phone'];
  
  	//just copying these (keeps the standard order)
  	$fields2['shipping'] = $fields['shipping'];
  	$fields2['account']  = $fields['account'];
  	$fields2['order']    = $fields['order'];
  
  	return $fields2;
  }