functions.php

<?php // don't include this line in your functions.php, since it already starts with it.

function fee_line_item_types( $types = array() ) {
	$types = array(
			'task' => __( 'Task', 'sprout-invoices' ),
			'service' => __( 'Service', 'sprout-invoices' ),
			'product' => __( 'Product', 'sprout-invoices' ),
			'fee' => __( 'Fees', 'sprout-invoices' ),
		);

	return $types;
}
add_filter( 'si_line_item_types',  'fee_line_item_types' );


function fee_type_options( $columns = array(), $type = 'fee' ) {
	if ( 'fee' === $type ) {
		$columns = array(
					'_id' => array(
							'type' => 'hidden',
							'value' => mt_rand(),
							'weight' => 0,
						),
					'desc' => array(
							'label' => __( 'Fees', 'sprout-invoices' ),
							'type' => 'textarea',
							'calc' => false,
							'hide_if_parent' => false,
							'weight' => 1,
						),
					'sku' => array(
							'type' => 'hidden',
							'placeholder' => '',
							'calc' => false,
							'numeric' => false,
							'weight' => 3,
						),
					'rate' => array(
							'label' => __( 'Amount', 'sprout-invoices' ),
							'type' => 'small-input',
							'calc' => false,
							'hide_if_parent' => true,
							'weight' => 5,
						),
					'qty' => array(
							'type' => 'hidden',
							'placeholder' => 1,
							'calc' => true,
							'hide_if_parent' => true,
							'weight' => 10,
						),
					'tax' => array(
							'label' => sprintf( '&#37; <span class="helptip" title="%s"></span>', __( 'A percentage adjustment per line item, i.e. tax or discount', 'sprout-invoices' ) ),
							'type' => 'hidden',
							'calc' => false,
							'hide_if_parent' => true,
							'weight' => 15,
						),
					'total' => array(
						'label' => __( 'Total', 'sprout-invoices' ),
						'type' => 'total',
						'placeholder' => sa_get_formatted_money( 0 ),
						'calc' => true,
						'hide_if_parent' => false,
						'weight' => 50,
					),
				);
	}

	return $columns;
}
add_filter( 'si_line_item_columns', 'fee_type_options', 10, 2 );