Magento: Set shipping address to billing address by default (but retain the possibility to change it)

This will set the delivery address to the billing address and with no other changes to the code, the user will still be able to change the delivery address by using the right menu. This simply updates the default behavior of what needs to be entered.

In “app/design/frontend/default/blank/template/checkout/onepage/billing.phtml”
Find the section that looks like:

123
124
125
126
127
128
129
130
131
132
    <?php if ($this->canShip()): ?>
        <li>
            <<input type="radio" name="billing[use_for_shipping]" id="billing:use_for_shipping_yes" value="1"<?php if ($this->isUseBillingAddressForShipping()) {?> checked="checked"<?php }?> onclick="$('shipping:same_as_billing').checked = true;" class="radio" /><label for="billing:use_for_shipping_yes"><?php echo  $this->__('Ship to this address') ?></label>
            <input type="radio" name="billing[use_for_shipping]" id="billing:use_for_shipping_no" value="0"<?php if (!$this->isUseBillingAddressForShipping()) {?> checked="checked"<?php }?> onclick="$('shipping:same_as_billing').checked = false;" class="radio" /><label for="billing:use_for_shipping_no"><?php echo $this->__('Ship to different address') ?></label>
        </li>
    <?php endif; ?>
    </ul>
    <?php if (!$this->canShip()): ?>
        <input type="hidden" name="billing[use_for_shipping]" value="1" />
    <?php endif; ?>

And simply replace it by;

123
124
    </ul>
    <input type="hidden" name="billing[use_for_shipping]" value="1" />