This is how tab config looks in - catalog.xml
<block type="catalog/product_view_description" name="product.description" as="description" template="catalog/product/view/description.phtml"> <action method="addToParentGroup"><group>detailed_info</group></action> <action method="setTitle" translate="value"><value>Product Details</value></action> </block> <block type="catalog/product_view_attributes" name="product.attributes" as="additional" template="catalog/product/view/attributes.phtml"> <action method="addToParentGroup"><group>detailed_info</group></action> <action method="addToParentGroup"><group>detailed_info</group></action> <action method="setTitle" translate="value"><value>Additional Information</value></action> </block> <block type="cms/block" name="payment_options_tab" as="payment_options_tab" template="catalog/product/view/custom_tab_content.phtml"> <action method="setBlockId"><block_id>payment_options_tab</block_id></action> <action method="addToParentGroup"><group>detailed_info</group></action> <action method="setTitle" translate="value"><value>Payment Options</value></action> </block> <block type="cms/block" name="shipping_calculator_tab" as="shipping_calculator_tab" template="catalog/product/view/custom_tab_content.phtml"> <action method="setBlockId"><block_id>shipping_calculator_tab</block_id></action> <action method="addToParentGroup"><group>detailed_info</group></action> <action method="setTitle" translate="value"><value>Shipping Calculator</value></action> </block>
content of - custom_tab_content.phtml