---
title: CartCompletionAction - Storefront API
description: The completion action to checkout a cart.
api_version: 2026-04
source_url:
  html: https://shopify.dev/docs/api/storefront/latest/unions/CartCompletionAction
  md: https://shopify.dev/docs/api/storefront/latest/unions/CartCompletionAction.md
---

# Cart​Completion​Action

union

The completion action to checkout a cart.

## Fields with this union

* [Cart​Completion​Action​Required.action](https://shopify.dev/docs/api/storefront/latest/objects/CartCompletionActionRequired#field-CartCompletionActionRequired.fields.action)

  OBJECT

  The required completion action to checkout a cart.

***

```graphql
union CartCompletionAction = CompletePaymentChallenge
```