## Overview
Affirm offers customers seamless pay over time options. To build an Affirm integration that best works for your business, see how things work behind the scenes of an Affirm transaction.
Affirm's basic process flow begins when the customer selects Affirm at checkout. The steps below represent what the customer experiences on the front-end, and how Affirm's integration handles the checkout on the back-end. Testing
## Transaction flow
Affirm transaction flow
### 1. Customer initiates a checkout
The Affirm checkout process begins when the customer selects Affirm as their payment method and submits a checkout.
### 2. Create, configure, and send the Checkout object
Once the `checkout` object has been configured with the consumer and cart info, trigger the `checkout.open()` function to initiate the Affirm application flow in either a redirect or iframe modal.
The `checkout` object is the data payload that gets POSTed to the Affirm API to initialize checkout and contains all the information about the customer's order.
| Parameter | Description |
`merchant`
<span style="color:red">required</span> | API Key, Success & Failure Callback |
`billing`
_optional_ | Name, Address, Phone, and Email |
`shipping`
<span style="color:red">required</span> | Name, Address, Phone, and Email |
`items`
<span style="color:red">required</span> | Item Objects; Price, Qty, SKU, and URL |
`metadata`
_optional_ | Additional details pertaining to the transaction |
`total`
<span style="color:red">required</span> | Include values for Shipping, Tax, and Total |
### 3. Collect customer information
After the customer goes through the Affirm flow to select and confirm their loan terms, we redirect the customer to your confirmation page defined in the `user_confirmation_url` property of the `checkout` object.
Next, we send an HTTP request with the `checkout_token` to your page so you can parse the response and store it.
### 4. Authorize the transaction and complete the order
#### Send an authorization request
Send an [Authorize Transaction](🔗) request by passing the `checkout_token`.
#### Verify the authorized amount
Affirm requires a verification on the merchant side that checks if the authorized amount matches the order total. This is a security measure to make sure that the transaction amount matches the order information prior to order confirmation. The authorized amount will be returned in the `transaction` object sent in the authorization response.
#### Complete the order
Store the `
id` from the `transaction` object, which is used for all future transaction actions, retrieved from the `Authorize Transactions` API response.Redirect the customer to the order confirmation page or display a confirmation message.
This completes the order so you can fulfill it.