Docs on single charges.

Author: taylorotwell

billing.md

@@ -3,6 +3,7 @@
 - [Introduction](#introduction)
 - [Configuration](#configuration)
 - [Subscribing To A Plan](#subscribing-to-a-plan)
+- [Single Charges](#single-charges)
 - [No Card Up Front](#no-card-up-front)
 - [Swapping Subscriptions](#swapping-subscriptions)
 - [Subscription Quantity](#subscription-quantity)
@@ -89,6 +90,29 @@ If you would like to specify additional customer details, you may do so by passi
 
 To learn more about the additional fields supported by Stripe, check out Stripe's [documentation on customer creation](https://stripe.com/docs/api#create_customer).
 
+<a name="single-charges"></a>
+## Single Charges
+
+If you would like to make a "one off" charge against a subscribed customer's credit card, you may use the `charge` method:
+
+	$user->charge(100);
+
+The `charge` method accepts the amount you would like to charge in the lowest denominator of the currency. So, for example, the example above will charge 100 cents, or $1.00, against the user's credit card.
+
+The `charge` method also accepts an array for its second argument, allowing you to pass any options you wish to the underlying Stripe charge creation:
+
+	$user->charge(100, [
+		'source' => $token,
+		'receipt_email' => $user->email,
+	]);
+
+The charge method will return `false` if the charge fails. This typically indicates the charge was denied:
+
+	if ( ! $user->charge(100))
+	{
+		// The charge was denied...
+	}
+
 <a name="no-card-up-front"></a>
 ## No Card Up Front