How to Add Custom Field in the One Page Checkout in Magento

Step: – 1
Add Custom Field into Billing Address tab of the Onepage Checkout in Frontend.
app\design\frontend\[Package_name]\[Theme_name]\template\checkout\onepage\billing.phtml

<li class="wide">
<label for="billing:jobtitle"><?php echo $this->__('Job Title') ?></label>
<div class="input-box">
<input type="text" id="billing:jobtitle" name="billing[jobtitle]" 

value="<?php echo $this->htmlEscape($this->getAddress()->getJobtitle()) ?>" 

title="<?php echo $this->__('Job Title') ?>" class="input-text" />
</div>
</li>

Step: – 2
Add Custom Field into Shipping Address tab of the Onepage Checkout in Frontend.
app\design\frontend\[Package_name]\[Theme_name]\template\checkout\onepage\shipping.phtml

<li class="wide">
<label for="shipping:jobtitle"><?php echo $this->__('Job Title') ?></label>
<div class="input-box">
<input type="text" id="shipping:jobtitle" name="shipping[jobtitle]" 

value="<?php echo $this->htmlEscape($this->getAddress()->getJobtitle()) ?>"

 title="<?php echo $this->__('Job Title') ?>" class="input-text" onchange="shipping.setSameAsBilling(false);" />
</div>
</li>

Step: – 3
Add Custom Field into Customer Address Edit tab in Frontend.
app\design\frontend\[Package_name]\[Theme_name]\template\customer\address\edit.phtml

<li class="wide">
<label for="jobtitle"><?php echo $this->__('Job Title') ?></label>
<div class="input-box">
<input type="text" name="jobtitle" id="jobtitle" title="<?php echo $this->__('Job Title') ?>" 

value="<?php echo $this->htmlEscape($this->getAddress()->getJobtitle()) ?>" class="input-text" />
</div>
</li>

Step: – 4

System->Configuration->Customers->Customer Configurations->Address Templates
Add following code in the “Text” Textarea.

{{depend prefix}}{{var prefix}} {{/depend}}{{var firstname}} {{depend middlename}}{{var middlename}} 

{{/depend}}{{var lastname}}{{depend suffix}} {{var suffix}}{{/depend}}
    {{depend company}}{{var company}}{{/depend}}
    {{depend jobtitle}}{{var jobtitle}}{{/depend}}
    {{if street1}}{{var street1}}
    {{/if}}
    {{depend street2}}{{var street2}}{{/depend}}
    {{depend street3}}{{var street3}}{{/depend}}
    {{depend street4}}{{var street4}}{{/depend}}
    {{if city}}{{var city}},  {{/if}}{{if region}}{{var region}}, 

{{/if}}{{if postcode}}{{var postcode}}{{/if}}
    {{var country}}
    T: {{var telephone}}
    {{depend fax}}F: {{var fax}}{{/depend}} 

Step: – 5

System->Configuration->Customers->Customer Configurations->Address Templates
Add following code in the “HTML” Textarea.

{{depend prefix}}{{var prefix}} {{/depend}}{{var firstname}} 

{{depend middlename}}{{var middlename}} {{/depend}}{{var lastname}}{{depend suffix}} {{var suffix}}{{/depend}}<br/>
{{depend company}}{{var company}}<br />{{/depend}}
{{depend jobtitle}}{{var jobtitle}}<br />{{/depend}}
{{if street1}}{{var street1}}<br />{{/if}}
{{depend street2}}{{var street2}}<br />{{/depend}}
{{depend street3}}{{var street3}}<br />{{/depend}}
{{depend street4}}{{var street4}}<br />{{/depend}}
{{if city}}{{var city}},  {{/if}}{{if region}}{{var region}}, 

{{/if}}{{if postcode}}{{var postcode}}{{/if}}<br/>
{{var country}}<br/>
{{depend telephone}}T: {{var telephone}}{{/depend}}
{{depend fax}}<br/>F: {{var fax}}{{/depend}} 

Step: – 6

System->Configuration->Customers->Customer Configurations->Address Templates
Add following code in the “PDF” Textarea.

{{depend prefix}}{{var prefix}} {{/depend}}{{var firstname}} 

{{depend middlename}}{{var middlename}} {{/depend}}{{var lastname}}{{depend suffix}} {{var suffix}}{{/depend}}|
{{depend company}}{{var company}}|{{/depend}}
{{depend jobtitle}}{{var jobtitle}}|{{/depend}}
{{if street1}}{{var street1}}
{{/if}}
{{depend street2}}{{var street2}}|{{/depend}}
{{depend street3}}{{var street3}}|{{/depend}}
{{depend street4}}{{var street4}}|{{/depend}}
{{if city}}{{var city}},  {{/if}}{{if region}}{{var region}}, 

{{/if}}{{if postcode}}{{var postcode}}{{/if}}|
{{var country}}|
{{depend telephone}}T: {{var telephone}}{{/depend}}|
{{depend fax}}<br />F: {{var fax}}{{/depend}}|

I have created the separate module for adding Custom Field into Billing and Shipping Address in Frontend and Backend of the Magento Store.
Step: – 7
app\etc\modules\Tdg_All.xml
First of all create file with above given name and put following code into that file.

<?xml version="1.0" encoding="UTF-8"?>
<config>
 <modules>
  <Tdg_Check>
   <active>true</active>
   <codePool>local</codePool>
  </Tdg_Check>
 </modules>
</config> 

Step: – 8
app\code\local\Tdg\Check\etc\ config.xml

<?xml version="1.0" encoding="UTF-8"?>
<config>
 <modules>
  <Tdg_Check>
   <version>1.0.0</version>
  </Tdg_Check>
 </modules>
 <admin>
  <fieldsets>
   <customer_dataflow>
    <jobtitle><billing>1</billing><shipping>1</shipping></jobtitle>
   </customer_dataflow>
  </fieldsets>
 </admin>
 <global>
  <models>
   <check>
    <class>Tdg_Check_Model</class>
   </check>
  </models>
  <resources>
   <check_setup>
    <setup>
     <module>Tdg_Check</module>
    </setup>
    <connection>
     <use>core_setup</use>
    </connection>
   </check_setup>
   <check_write>
    <connection>
     <use>core_write</use>
    </connection>
   </check_write>
   <check_read>
    <connection>
     <use>core_read</use>
    </connection>
   </check_read>
  </resources>
  <fieldsets>
   <sales_copy_order_billing_address>
    <jobtitle><to_order>*</to_order></jobtitle>
   </sales_copy_order_billing_address>
   <sales_copy_order_shipping_address>
    <jobtitle><to_order>*</to_order></jobtitle>
   </sales_copy_order_shipping_address>
   <sales_convert_quote_address>
    <jobtitle><to_order_address>*</to_order_address><to_customer_address>*</to_customer_address></jobtitle>
   </sales_convert_quote_address>
   <sales_convert_order_address>
    <jobtitle><to_quote_address>*</to_quote_address></jobtitle>
   </sales_convert_order_address>
   <customer_address>
    <jobtitle><to_quote_address>*</to_quote_address></jobtitle>
   </customer_address>
   <checkout_onepage_billing>
    <jobtitle><to_customer>*</to_customer></jobtitle>
   </checkout_onepage_billing>
  </fieldsets>
 </global>
</config> 

Step: – 9
app\code\local\Tdg\Check\sql\check_setup\ mysql4-install-1.0.0.php

<?php
 /* @var $installer Mage_Customer_Model_Entity_Setup */
    $installer = $this;
    $installer->startSetup();
    /* @var $addressHelper Mage_Customer_Helper_Address */
    $addressHelper = Mage::helper('customer/address');
    $store         = Mage::app()->getStore(Mage_Core_Model_App::ADMIN_STORE_ID);

    /* @var $eavConfig Mage_Eav_Model_Config */
    $eavConfig = Mage::getSingleton('eav/config');

    // update customer address user defined attributes data
    $attributes = array(
        'jobtitle'           => array(
            'label'    => 'Job Title',
            'backend_type'     => 'varchar',
            'frontend_input'    => 'text',
            'is_user_defined'   => 1,
            'is_system'         => 0,
            'is_visible'        => 1,
            'sort_order'        => 140,
            'is_required'       => 1,
            'multiline_count'   => 0,
            'validate_rules'    => array(
                'max_text_length'   => 255,
                'min_text_length'   => 1
            ),
        ),
    );

    foreach ($attributes as $attributeCode => $data) {
        $attribute = $eavConfig->getAttribute('customer_address', $attributeCode);
        $attribute->setWebsite($store->getWebsite());
        $attribute->addData($data);
            $usedInForms = array(
                'adminhtml_customer_address',
                'customer_address_edit',
                'customer_register_address'
            );
            $attribute->setData('used_in_forms', $usedInForms);
        $attribute->save();
    }

    $installer->run("
        ALTER TABLE {$this->getTable('sales_flat_quote_address')} 

ADD COLUMN `jobtitle` VARCHAR(255) CHARACTER SET utf8 DEFAULT NULL AFTER `fax`;
         ALTER TABLE {$this->getTable('sales_flat_order_address')} 

ADD COLUMN `jobtitle` VARCHAR(255) CHARACTER SET utf8 DEFAULT NULL AFTER `fax`;
        ");
    $installer->endSetup();
?>