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Checkout API call sequence from start checkout to place order

Key Takeaway

Start checkout, poll GET until it returns 200, then send your PATCH updates, submit payment, and place the order. A PATCH sent while background processing is still running returns 409 Conflict.

The Commerce Checkout APIs let a B2B or D2C storefront, including a custom or headless one, run checkout as a series of REST calls against a checkout session tied to a cart. To build or debug a checkout, you need to know which call triggers which calculator, and which status codes mean wait, retry, or failure.

How to run a checkout

All checkout resources live under /commerce/webstores/{webstoreId}/checkouts. Most of them take {activeOrCheckoutId} in the path, so you can pass the literal value active or a specific checkout ID.

Calculator: A process that runs in the background and handles one part of checkout, such as pricing, promotions, inventory, shipping, or tax.

A typical buyer journey runs in this order:

Review the cart items with a GET on the Cart Items resource.
Start checkout.
Wait for the background calculators to finish.
Update contact and shipping details with PATCH.
Pick a delivery method with PATCH.
Submit payment with POST .../payments.
Place the order with POST .../orders or POST .../orders/actions.

Salesforce Accredited B2B Commerce Developer Professional Study Guide

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Customize existing checkout flows in order to address the most common customer needs and provide an optimal Storefront experience

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Custom checkout versus managed checkout for B2B stores

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Building a custom checkout flow for an Aura store

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CartCheckoutSession state and checkout session flow actions

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Commerce category cart flow actions and Aura store support

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B2B Commerce checkout flow core actions for cart calculations

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Draft order creation and activation in a B2B checkout flow

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Custom LWC screen components in an Aura checkout flow

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LWR checkout page layouts and checkout sections

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Payment section configuration on the LWR checkout page

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Replacing legacy checkout components in older LWR stores

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Enabling guest checkout in a B2B store

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Checkout API call sequence from start checkout to place order

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Background calculators triggered by checkout API calls

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Handling asynchronous checkout responses before custom logic runs

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Cart edits during an active checkout and simplified cart cleanup

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Place order APIs with and without Streamlined Place Order

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Asynchronous order placement and the Retrigger Place Order flow

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Record-triggered Order automation and duplicate B2B orders

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Shipping to multiple addresses in custom checkout

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Commerce reference implementation samples as integration templates
Salesforce native services versus third-party shipping, tax and payment
Commerce extensions versus the checkout integrations framework
Checkout events that trigger integration and calculator runs
Custom Cart Calculate orchestrator and default calculator sequence
BuyerActions versus BuyerActionDetails in calculator logic
Extending default cart calculators in Apex
Pricing reference implementation for cart items
Inventory check reference implementation and inventory reservation
Shipping calculation reference implementation
Tax calculation reference implementation
Surfacing calculation errors with CartValidationOutput
Aura checkout integration Apex interfaces and IntegrationStatus
Registering and mapping a custom integration or extension to a store
Unit testing cart calculators and integration classes
Commerce payment architecture and payment framework responsibilities
Payment gateway adapter class structure and request types
Synchronous versus asynchronous payment gateway adapters
Checkout Payments API request types and payment tokens
Server-side versus client-side payment processing
PostAuth handling in a client-side payment gateway adapter
Payment resubmission and cart-change invalidation in checkout
Scope limits of checkout payment processing

LWR versus Aura store component support
Building block components on LWR store pages
Standard LWR store component capabilities and limits
Open source components versus building a custom replacement
Exposing a custom component's properties in Experience Builder
Branding LWR store components with styling hooks versus custom CSS classes
Wire service syntax and reactive parameters in store components
Child events and parent-to-child property binding in store components
Expressions and data providers in Commerce component properties
Data expressions for product, cart, search and order page components
Conditional rendering with lwc:if and lwc:else
Expression-based visibility versus component variations
Faster Add-to-Cart impact on custom cart components

Anatomy of a custom storefront LWC and base components
SFDX workflow for creating and deploying a custom store component
Placing a custom component on an LWR store page
Store and buyer context in custom components
Imperative APIs, wire adapters, and Storefront Actions compared
Storefront APIs versus UI API and Aura controllers
Data access priority for custom storefront components
Cart and coupon operations with commerce/cartApi
Dispatching Storefront Actions from a custom component
Handling expression-bound data in custom components
Data provider expressions by store page
Custom pricing component showing a discount percentage
Backend-for-frontend Apex controllers using Commerce ConnectApi
Cacheable Apex controllers for custom storefront components
Custom header or footer components and the commerce custom layout
Custom checkout component in an LWR store
Custom payment component for LWR checkout
Third-party scripts and head markup in an LWR store

WebStore as the hub of the B2B Commerce data model
Default records created with a new B2B store
Store-to-catalog relationship and catalog capacity
Product category hierarchy and product-to-category assignment
Product2 records and the product variation data model
Product bundles versus product sets
BuyerAccount records and enabling accounts as buyers
Buyer group membership and store assignment objects
Buyer, buyer manager and account switcher access
Buyer billing and shipping address records
Entitlement policy objects and product and price visibility
Standard, store, strikethrough and buyer group price books
Store pricing strategy and price resolution across buyer groups
Tiered and volume pricing data model
Dynamic buyer group assignment with the Buyer Group extension
Guest browsing and self-registration for a B2B store
Store CMS workspace and public channel for imports
Linking CMS images and attachments to product records
Commerce CSV import versus Data Loader and import APIs
Price book and entitlement handling during commerce import
Rebuilding the search index after catalog data changes
WebCart and its related cart objects
Cart-to-order conversion and Order Summary records
Aura versus LWR store integration architecture
Registering a custom Apex integration and mapping it to a store
StoreIntegratedService Integration and ServiceProviderType values
Named credentials for integration callouts
LWR checkout integration triggers and payment processing
Payment gateway records and store mapping

Debug logs and trace flags for storefront Apex transactions
CommerceDiagnosticEvent for monitoring Commerce activity
Root causes when a buyer cannot see or find a product
Troubleshooting Assistant for product visibility issues
Buyer access failures and Commerce permission sets
Checkout API status codes and polling for calculator completion
Checkout API sequencing after payment and billing entry
CartCheckoutSession creation by custom logic versus the Checkout API
'We Can't Find Checkout' error after cart changes
Concurrent cart modification and checkout conflict errors
Custom calculator price fields and $NaN order summary amounts
Missing delivery methods and CartValidationOutput in custom calculators
Out-of-stock errors when inventory is available
Checkout phone number E.164 validation
Payment Method Isn't Authorized error diagnosis
Payments created but not reflected on WebCart
Place Order API versus Place Order Action API for webhook-confirmed payments
cartToOrderSummary compatibility with the Place Order Action API
Diagnosing orders and order summaries that are not created
CartItem to OrderItem ListPrice mapping
Order failure management for pending and failed orders
High Scale Orders and order ingestion troubleshooting

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Checkout API call sequence from start checkout to place order

Key Takeaway

Start checkout, poll GET until it returns 200, then send your PATCH updates, submit payment, and place the order. A PATCH sent while background processing is still running returns 409 Conflict.

The Commerce Checkout APIs let a B2B or D2C storefront, including a custom or headless one, run checkout as a series of REST calls against a checkout session tied to a cart. To build or debug a checkout, you need to know which call triggers which calculator, and which status codes mean wait, retry, or failure.

How to run a checkout

All checkout resources live under /commerce/webstores/{webstoreId}/checkouts. Most of them take {activeOrCheckoutId} in the path, so you can pass the literal value active or a specific checkout ID.

Calculator: A process that runs in the background and handles one part of checkout, such as pricing, promotions, inventory, shipping, or tax.

A typical buyer journey runs in this order:

Review the cart items with a GET on the Cart Items resource.
Start checkout.
Wait for the background calculators to finish.
Update contact and shipping details with PATCH.
Pick a delivery method with PATCH.
Submit payment with POST .../payments.
Place the order with POST .../orders or POST .../orders/actions.