> For the complete documentation index, see [llms.txt](https://loop-crypto.gitbook.io/old-loop-crypto/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://loop-crypto.gitbook.io/old-loop-crypto/technical-docs/sample-guide-collect-a-subscription-or-one-time-payment.md).

# Sample guide: Collect a subscription or one-time payment

Collecting crypto subscriptions on-chain can be done in 4 simple steps. 

1. Create an [item](/old-loop-crypto/technical-docs/apis/items.md) 
2. Collect authorization via [checkout page](#checkout-page) or [widget](#checkout-widget)
3. Invoice (i.e. schedule payment) by creating a [transfer request](/old-loop-crypto/technical-docs/apis/transfer-requests.md)
4. Configuring [webhooks](/old-loop-crypto/technical-docs/apis/webhooks.md) and granting access
5. Handling cancellations 

## Using our SDK 

### 1. Create a subscription 

You can use our create [`POST items`](/old-loop-crypto/technical-docs/apis/items/adding-items.md) endpoint to configure subscriptions in Loop. A subscription is denoted with a [`type`](/old-loop-crypto/technical-docs/apis/items/adding-items/item-types.md) `= 2`  and a one-time payment has a `type=2` and a `frequencyCount = 0.`

These items will appear on the company dashboard and can also be managed there. 

## 2. Collecting authorization 

Companies have two ways to collect authorization: use Loop's checkout page or add Loop’s checkout widget to your website. 

#### **Checkout page** 

Loop provides a custom [checkout page](/old-loop-crypto/technical-docs/archeticture/collecting-authorization/checkout-page.md) for each item with the type of "subscription, donation, and fee". This page can be sent directly to the end customer via email, telegram, or an externally generated invoice or it can be embedded directly on your site in a "[pay with crypto](/old-loop-crypto/technical-docs/archeticture/collecting-authorization/checkout-page/add-pay-with-crypto-button.md)" button. 

#### Checkout widget

For those that prefer, Loop provides [checkout widget](#checkout-modal) that can be integrated in the context of your company's website or application, to enable your customers to pay with crypto. The modal allows end users to give Loop authorization to enable autopay. 

## 3. Invoice

Once you have authorization to bill a customer, you can then schedule payments. You can choose to auto-invoice or bill manually. 

#### Auto-invoicing

*This is best for companies that have fixed payment amounts and dates (i.e. $30/mo every month).* 

Loop will automatically generate the next invoice for subscriptions and one-time payments with [auto-invoicing](/old-loop-crypto/dashboard-functionality/subscriptions/auto-invoicing.md) enabled based on the item's payment frequency and amount specified.

#### Manually  

*This is best for companies who may have changing payment amounts and dates and thus require flexibility in scheduling payments or are using Loop to schedule outbound payments.* 

Companies can generate an invoice (called a [transfer requests](/old-loop-crypto/technical-docs/apis/transfer-requests.md)) manually using the [`POST Transfers`](/old-loop-crypto/technical-docs/apis/transfer-requests.md) call.  

### 4. Configuring webhooks and granting access  

Loop uses [webhooks](/old-loop-crypto/technical-docs/apis/webhooks.md) to notify you of events. You can configure these webhooks by simply providing an endpoint.

The `AgreementSignedUp` event lets you know that a wallet provided authorization to be billed - it does not mean you have been paid yet, but it does indicate the user has set an allowance for payments. 

The `TransferProcessed` event is the payment notification and indicates funds have been sent to the receiving wallet.

The `AgreementCancelled` event is the notification that indicates a customer has cancelled their subscription. See below for more details on cancellations. 

#### Granting access

You can use the `wallet address,` `email, or` `a reference ID` provided in either of these events to provide access to your system. 

Even with immediate invoicing, there will be a delay between the webhook events, as the transaction must be confirmed on-chain. Companies can decide to grant access based on the `AgreementSignedUp` event and take action if you do not hear about the `TransferProcessed` event within a certain amount of time, (e.g. show a warning, etc). We built Loop to be flexible, so companies can decide how "aggressive" they want to be about payment confirmation. 

There are a few reasons why the `TransferProcessed` event would not occur:

* The wallet does not have enough balance to cover the payment 
* The wallet does not have enough token allowance to cover the payment 
* The transaction is stuck in the mempool 
* Loop's relay network is down 

Wallet amount and balance information can be found on our company dashboard for all active subscribers if you are troubleshooting a late payment. 

## 5. Cancellations  

Customers can cancel a subscription either: 

1. directly with the end company, who then can tell Loop about the cancellation via the [`PATCH agreements`](/old-loop-crypto/technical-docs/apis/agreements.md) call, or
2. the customer can cancel directly on  [Loop's Portal](https://my.loopcrypto.xyz/login). 

Regardless of method, Loop will emit a `AgreementCancelled` events that can be used to manage the end customer's access. 

When a subscription is canceled, all future scheduled invoices will be cancelled but any currently due invoices will not be. Companies can cancel these scheduled payments using the [`PATCH Transfer`](/old-loop-crypto/technical-docs/apis/transfer-requests/canceling-transfer-requests.md) call.