We'd like to find a payment provider that lets us do something similar to Hailo, ie:
Users sign up and give us their credit card details/authorise us to charge their account. They only need to do this once.
In Hailo's case, users might take a cab journey at any time and be billed any amount (within reason). In our case, users might need a job done at any time, again with an invoice for an arbitrary amount.
So ideally we'd be able to charge users accounts at any time, for any amount, without further authorisation. This is possible because Hailo (and I believe Uber) have it implemented. However, I don't know if they use a third-party payment provider or rolled their own.
Something like BrainTree's recurring payments is close to what we want, but not exactly. We want to be able to bill at arbitrary times, not on a fixed schedule.
The best option we currently have is to use recurring billing, ie save invoices and then charge them all at once at the end of the month. This isn't ideal from a cashflow -perspective, though. Another option is to use GoCardless' variable billing, (you ask customers permission to bill up to £X per month), though from speaking to people it seems they'd be leary of that as it seems like an upfront commitment.
Can we do it our way? How do companies like Hailo and Uber do it?
We're in the UK, by the way.
In PayPal world - we call this kind of functionality as Reference Transactions - here are the 2 how-tos that would give you more info on how to implement reference transactions with PayPal accounts and direct credit cards:
You can also use our Preapproval functionality - which would give you delegated access to a PayPal account to make payments on behalf of them. Here is it's how-to.
Full disclosure, I work as a developer for Braintree.
Using Braintree you can create transactions at any time, not just on a recurring basis. In fact Uber is a Braintree customer. You would store the card in the Braintree vault and create a new transaction when you are ready to bill the customers credit card.
Braintree has recently announced an international expansion that will support merchants in the UK and other countries in the next few months.
From your description Authorize.net CIM will do the job - http://www.authorize.net/solutions/merchantsolutions/merchantservices/cim/
It's PCI compliant and let you store your customer credit card details with them and return a token for the customer. Then you can use this token to charge customer credit card whenever you need. Also their recurring billing facility would let you charge a fixed recurring charge if needed - http://www.authorize.net/solutions/merchantsolutions/merchantservices/automatedrecurringbilling/
DataCash will let you do this, amongst many, many other things. You just provide their 16-digit reference number in the XML rather than a card number.
(Note: I'm an ex-DataCash employee, and we use DataCash as a payment gateway at my current work.)
来源：https://stackoverflow.com/questions/11477086/recurring-payments-with-arbitrary-amounts-and-at-arbitrary-times