> ## Documentation Index
> Fetch the complete documentation index at: https://supertab-feature-merchant-auth-change-again.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Supertab.checkout

> Methods reference for `Supertab.checkout`

`Supertab.checkout` client handles the checkout flow for purchases requiring payment.

## Methods

### `start`

Starts the checkout process. Whenever the purchase requires payment (i.e. the tab reaches the limit or the purchased offering is of a "pay now" type),
use this method to start the checkout flow and allow user to pay for the tab.

The payment is completed in a a popup with Supertab checkout app. Supertab.js uses [postMessage](https://developer.mozilla.org/en-US/docs/Web/API/Window/postMessage) for signaling payment status back to the parent window.

<Info>
  Since this method opens a popup, it should be called in response to a user action, e.g. a button click.
</Info>

#### Parameters

<ParamField path="checkoutUrl" type="string" required>
  The URL of the checkout page found in `actionRequiredDetails` object of the [`Supertab.api.purchase`](/supertab-js/reference/api#purchase) response.
</ParamField>

#### Returns

Boolean. `true` if the checkout was completed successfully, `false` otherwise (e.g. when the user closes the popup or cancels the payment).

#### Example

```typescript Make a purchase and get the checkout URL theme={null}
const purchaseResponse = await supertabClient.api.purchase({
    offeringId: "test.offering-id"
});

const checkoutUrl = purchaseResponse.actionRequiredDetails.next;
```

```javascript Start the checkout process theme={null}
<button onClick={
    () => supertabClient.checkout.start(checkoutUrl)
}>Pay</button>
```