"Fast Trak" style subscription?

[Pat McClellan]

How can I set up Stripe to handle "Fast Trak" style subscriptions? Fast Trak (called other things in various cities) is the the device in your car that allows automatic payment as you pass through a toll booth. With a Fast Trak account, you pre-pay $50, and your account is debited each time you pass through the toll booth. When your balance drops to $10, the account is re-charged to bring the balance back to $50.

My app is a transaction-based service, with each transaction costing only 3-5 cents. I want customers to establish an account with a $50 charge, which establishes an account balance. Each transaction is debited to the account, and the customer is re-charged when the balance drops below $10. This is not monthly -- the period will vary based on usage.

I can't find a description or even a name for this kind of plan.

Advice?

[Remi J.]

Hey Pat,

Usually, this is something that you would build on your end as it's not really a subscription-based model.

The idea here is that a customer signs up for your service and can fill their balance on their account. In your example, you charge them $50 and you keep track of their balance in your database. Every time they make a transaction on your service, you decrease their balance by the expected amount. If the balance goes below a certain threshold ($10) you then call the Create Charge API [1] to charge them the expected amount. If the charge succeeds, you increase their balance by the charge amount. If it fails, you email them to warn them about their low balance and ask them to come update their card details.

If you don't want to store this in your own database, you could use the `account_balance` property [2] on the Customer object [3]. You'd have to be careful in that case to avoid two separate requests trying to update the account balance at the same time as those calls are not atomic in Stripe. Otherwise a customer could use your service twice in the same second for example and you'd end up assuming the balance was $42 in both cases for example and incorrectly.

As for the name for this kind of "plan", I hadn't heard of "Fast Trak" and instead usually call this a "Pay as you go" service. It's fairly common in cities with public transportation such as London with the Oyster card. Hopefully you might get a bit more information or examples based on this other name.

Hope this helps!

Remi

[1] https://stripe.com/docs/api#create_charge

[2] https://stripe.com/docs/api#customer_object-account_balance

[3] https://stripe.com/docs/api#customer_object

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