Add Company column in customer Grid Magento Backend
Go to /app/code/core/Mage/Adminhtml/Block/Customer/Grid.php
in _prepareCollection() add following file
->joinAttribute('billing_company', 'customer_address/company', 'default_billing', null, 'left')
and in _prepareColumns() add following code,
$this->addColumn('company', array(
'header' => Mage::helper('customer')->__('Company'),
'index' => 'billing_company'
));
Note: its the best practise that dont make any changes in your core file. overwrite your php file in local and then make any changes.
