# Flex Documentation

## Docs

- [List Balance Transactions](https://docs.withflex.com/api-reference/balance-transactions/list-balance-transactions.md): Returns a list of Balance transactions.
- [Get Capture](https://docs.withflex.com/api-reference/captures/get-capture.md): Get a capture by ID
- [List Captures](https://docs.withflex.com/api-reference/captures/list-captures.md): List captures
- [Update Capture](https://docs.withflex.com/api-reference/captures/update-capture.md): Update a capture by ID
- [Cancel Auth Checkout Session](https://docs.withflex.com/api-reference/checkout-sessions/cancel-auth-checkout-session.md): Cancel authorization on payment intents for a checkout session
- [Capture Checkout Session](https://docs.withflex.com/api-reference/checkout-sessions/capture-checkout-session.md): Capture a Checkout Session.
- [Create Checkout Session](https://docs.withflex.com/api-reference/checkout-sessions/create-checkout-session.md): Creates a Checkout Session object.
- [Get Checkout Session](https://docs.withflex.com/api-reference/checkout-sessions/get-checkout-session.md): Retrieves a Session object.
- [Get Line Items](https://docs.withflex.com/api-reference/checkout-sessions/get-line-items.md): Returns a list of line items corresponding to a checkout session.
- [List Checkout Sessions](https://docs.withflex.com/api-reference/checkout-sessions/list-checkout-sessions.md): Returns a list of Checkout Sessions.
- [Preview Capture Allocation](https://docs.withflex.com/api-reference/checkout-sessions/preview-capture-allocation.md): Preview how a capture would be allocated across payment methods.
- [Preview Refund Allocation](https://docs.withflex.com/api-reference/checkout-sessions/preview-refund-allocation.md): Preview how a refund would be allocated across payment methods.
- [Reauth Checkout Session](https://docs.withflex.com/api-reference/checkout-sessions/reauth-checkout-session.md): Reauth a Checkout Session.
- [Refund Checkout Session](https://docs.withflex.com/api-reference/checkout-sessions/refund-checkout-session.md): Refund a Checkout Session.
- [Resend Checkout Session Lomn](https://docs.withflex.com/api-reference/checkout-sessions/resend-checkout-session-lomn.md): Resends existing LOMN (Letter of Medical Necessity) emails for a checkout session.
- [Resend Checkout Session Receipts](https://docs.withflex.com/api-reference/checkout-sessions/resend-checkout-session-receipts.md): Resends existing receipt emails for a checkout session.
- [Create Coupon](https://docs.withflex.com/api-reference/coupons/create-coupon.md): Create a coupon
- [Get Coupon](https://docs.withflex.com/api-reference/coupons/get-coupon.md): Get a coupon by id
- [List Coupons](https://docs.withflex.com/api-reference/coupons/list-coupons.md): List coupons
- [Create Customer](https://docs.withflex.com/api-reference/customers/create-customer.md): Create a new Customer
- [Delete Customer](https://docs.withflex.com/api-reference/customers/delete-customer.md): Delete a customer
- [Get Customer](https://docs.withflex.com/api-reference/customers/get-customer.md): Get a single customer
- [Get Customer Payment Method](https://docs.withflex.com/api-reference/customers/get-customer-payment-method.md): Get a single payment method
- [List Customer Payment Methods](https://docs.withflex.com/api-reference/customers/list-customer-payment-methods.md): List all payment methods for a single customer
- [List Customers](https://docs.withflex.com/api-reference/customers/list-customers.md): List all customers
- [Update Customer](https://docs.withflex.com/api-reference/customers/update-customer.md): Update a customer
- [Close Dispute](https://docs.withflex.com/api-reference/disputes/close-dispute.md): Close a dispute, accepting the dispute and forfeiting the funds.
- [Count Disputes](https://docs.withflex.com/api-reference/disputes/count-disputes.md): Returns the count of disputes that require a response.
- [Get Dispute](https://docs.withflex.com/api-reference/disputes/get-dispute.md): Retrieves the dispute with the given ID.
- [List Disputes](https://docs.withflex.com/api-reference/disputes/list-disputes.md): Returns a list of disputes.
- [Update Dispute](https://docs.withflex.com/api-reference/disputes/update-dispute.md): Update the evidence of a dispute.
- [Retry Event](https://docs.withflex.com/api-reference/events/retry-event.md): Retry sending an exisitng event
- [Expanding Resources](https://docs.withflex.com/api-reference/expanding-resources.md): Learn how to request expanded responses with additional information about related objects.
- [Cancel Export](https://docs.withflex.com/api-reference/exports/cancel-export.md): Cancel a new export function
- [Create Export](https://docs.withflex.com/api-reference/exports/create-export.md): Creates a new export function
- [Create Export Url](https://docs.withflex.com/api-reference/exports/create-export-url.md): Creates a new export function
- [Get Export](https://docs.withflex.com/api-reference/exports/get-export.md): Retrieves the export details with the given ID.
- [List Exports](https://docs.withflex.com/api-reference/exports/list-exports.md): Returns a list of exports for the authenticated partner.
- [Create File](https://docs.withflex.com/api-reference/files/create-file.md): Upload a file (JPEG, PNG, or PDF, max 5MB) for use as dispute evidence.
- [List Files](https://docs.withflex.com/api-reference/files/list-files.md): Returns a list of files. The files are returned sorted by creation date, with the most recently created files appearing first.
- [Retrieve File](https://docs.withflex.com/api-reference/files/retrieve-file.md): Returns a file object for the file with the specified ID.
- [Introduction to the Flex API](https://docs.withflex.com/api-reference/introduction.md): Learn the basics of integrating with the Flex API to accept HSA/FSA payments
- [Get Invoice](https://docs.withflex.com/api-reference/invoices/get-invoice.md): Get an invoice by id
- [List Invoices](https://docs.withflex.com/api-reference/invoices/list-invoices.md): List invoices
- [Mark Invoice Uncollectible](https://docs.withflex.com/api-reference/invoices/mark-invoice-uncollectible.md): Mark an invoice as uncollectible. This will stop automatic collection attempts and move the associated subscription to an unpaid state.
- [Get Letters For Order](https://docs.withflex.com/api-reference/letters/get-letters-for-order.md): Lists the letters for the given checkout session
- [Stream Letter Data](https://docs.withflex.com/api-reference/letters/stream-letter-data.md): Streams the binary data for the given letter
- [Get Order](https://docs.withflex.com/api-reference/orders/get-order.md): Gets the order by id
- [Get Product Eligibility For Order Line Item](https://docs.withflex.com/api-reference/orders/get-product-eligibility-for-order-line-item.md): Gets product eligibility rationale for a product in an order's line item
- [List Line Items For Order](https://docs.withflex.com/api-reference/orders/list-line-items-for-order.md): Lists the line items for the given order
- [List Orders](https://docs.withflex.com/api-reference/orders/list-orders.md): Gets the list of orders for the given user
- [Cancel Payment Intent](https://docs.withflex.com/api-reference/payment-intents/cancel-payment-intent.md): Cancels a PaymentIntent
- [Get Payment Intent](https://docs.withflex.com/api-reference/payment-intents/get-payment-intent.md): Retrieves the details of a PaymentIntent that has previously been created.
- [List Payment Intents](https://docs.withflex.com/api-reference/payment-intents/list-payment-intents.md): Returns a list of payment intents
- [Send Receipt](https://docs.withflex.com/api-reference/payment-intents/send-receipt.md): Send a receipt to customer for the associated payment
- [Create Payment Link](https://docs.withflex.com/api-reference/payment-links/create-payment-link.md): Creates a new payment link
- [Get Payment Link](https://docs.withflex.com/api-reference/payment-links/get-payment-link.md): Return a payment link by ID
- [List Payment Links](https://docs.withflex.com/api-reference/payment-links/list-payment-links.md): Returns a list of your payment links
- [Update Payment Link](https://docs.withflex.com/api-reference/payment-links/update-payment-link.md): Partially updates an existing payment link
- [List Payouts](https://docs.withflex.com/api-reference/payouts/list-payouts.md): Returns a list of payouts.
- [Create Price](https://docs.withflex.com/api-reference/prices/create-price.md): Creates a new price for an existing product. The price can be recurring or one-time.
- [Get Price](https://docs.withflex.com/api-reference/prices/get-price.md): Retrieves the price with the given ID.
- [List Prices](https://docs.withflex.com/api-reference/prices/list-prices.md): Returns a list of your prices.
- [Update Price](https://docs.withflex.com/api-reference/prices/update-price.md): Updates the specified price by setting the values of the parameters passed. Any parameters not provided are left unchanged.
- [Create Product](https://docs.withflex.com/api-reference/products/create-product.md): Creates a new product.
- [Get Product](https://docs.withflex.com/api-reference/products/get-product.md): Returns a product object for the product with the specified ID.
- [List Products](https://docs.withflex.com/api-reference/products/list-products.md): Returns a list of your products. The products are returned sorted by creation date, with the most recently created products appearing first.
- [Update Product](https://docs.withflex.com/api-reference/products/update-product.md): Updates the specified product by setting the values of the parameters passed. Any parameters not provided will be left unchanged.
- [Create Promo Code](https://docs.withflex.com/api-reference/promo-codes/create-promo-code.md): Create a promo code
- [Get Promo Code](https://docs.withflex.com/api-reference/promo-codes/get-promo-code.md): Retrieve a promo code by id
- [List Promo Codes](https://docs.withflex.com/api-reference/promo-codes/list-promo-codes.md): List promo codes
- [Update Promo Code](https://docs.withflex.com/api-reference/promo-codes/update-promo-code.md): Update a promo code by id
- [Get Receipt For Order](https://docs.withflex.com/api-reference/receipts/get-receipt-for-order.md): Lists the receipts for the given consumer
- [Create Refund](https://docs.withflex.com/api-reference/refunds/create-refund.md): Creates a new refund object and refund the specified payment.
- [Get Refund](https://docs.withflex.com/api-reference/refunds/get-refund.md): Retrieves the details of an existing refund.
- [List Refunds](https://docs.withflex.com/api-reference/refunds/list-refunds.md): Returns a list of all refunds you've previously created. The refunds can be filtered by status, payment_intent, or checkout_session.
- [Update Refund](https://docs.withflex.com/api-reference/refunds/update-refund.md): Updates an existing refund object.
- [Get Review](https://docs.withflex.com/api-reference/reviews/get-review.md): Retrieves the details of a Stripe Radar review.
- [List Reviews](https://docs.withflex.com/api-reference/reviews/list-reviews.md): Returns a list of Stripe Radar reviews for the authenticated partner.
- [Create Setup Intent](https://docs.withflex.com/api-reference/setup-intents/create-setup-intent.md): Creates a new setup intent for collecting payment method details.
- [Get Setup Intent](https://docs.withflex.com/api-reference/setup-intents/get-setup-intent.md): Retrieves the setup intent with the given ID.
- [List Setup Intents](https://docs.withflex.com/api-reference/setup-intents/list-setup-intents.md): Returns a list of your setup intents.
- [Create Shipping Rate](https://docs.withflex.com/api-reference/shipping-rates/create-shipping-rate.md): Creates a new shipping rate object
- [Get Shipping Rate](https://docs.withflex.com/api-reference/shipping-rates/get-shipping-rate.md): Returns the shipping rate object with the given ID.
- [List Shipping Rates](https://docs.withflex.com/api-reference/shipping-rates/list-shipping-rates.md): Returns a list of your shipping rates
- [Update Shipping Rate](https://docs.withflex.com/api-reference/shipping-rates/update-shipping-rate.md): Updates the specified shipping rate by setting the values of the parameters passed. Any parameters not provided will be left unchanged.
- [Cancel Subscription](https://docs.withflex.com/api-reference/subscriptions/cancel-subscription.md): Cancels a customer's subscription. If `cancel_at_period_end` is true, the subscription will be canceled at the end of the current billing period. Otherwise, the subscription is canceled immediately.
- [Get Refund Preview](https://docs.withflex.com/api-reference/subscriptions/get-refund-preview.md): Previews the prorated refund amount for a subscription cancellation.
- [Get Subscription](https://docs.withflex.com/api-reference/subscriptions/get-subscription.md): Retrieves the subscription with the given ID.
- [List Subscriptions](https://docs.withflex.com/api-reference/subscriptions/list-subscriptions.md): Returns a list of subscriptions.
- [Resend Subscription Receipts](https://docs.withflex.com/api-reference/subscriptions/resend-subscription-receipts.md): Resends existing receipt emails for the initial checkout of a subscription.
- [Update Subscription](https://docs.withflex.com/api-reference/subscriptions/update-subscription.md): Updates an existing subscription to match the specified parameters.
- [Flex Refund API Guide](https://docs.withflex.com/api-refund-best-practices.md)
- [Product Updates](https://docs.withflex.com/changelog.md): Keep track of all the latest updates and improvements to Flex.
- [Invite Users](https://docs.withflex.com/developer-guides/dashboard/invite-users.md): Learn how to invite new members to your organization to access the partner dashboard and private documentation.
- [Manage Your Customers](https://docs.withflex.com/developer-guides/dashboard/manage-customers.md): Learn how to view and manage customer information through the Flex dashboard.
- [Manage Your HSA/FSA Payments](https://docs.withflex.com/developer-guides/dashboard/manage-hsa-fsa-payments.md): Learn how to view, export, and refund HSA/FSA payments through the Flex dashboard.
- [Manage Your Products and Prices](https://docs.withflex.com/developer-guides/dashboard/manage-products-and-prices.md): Learn how to view and manage your products and prices through the Flex dashboard.
- [Get Insights Into HSA/FSA as a Channel](https://docs.withflex.com/developer-guides/dashboard/overview.md): Understand HSA/FSA payment trends and performance through the Flex Dashboard.
- [Off Session Checkouts With a Product Requiring a Letter](https://docs.withflex.com/developer-guides/integration/checkout/example-walkthrough.md)
- [Fulfill Orders](https://docs.withflex.com/developer-guides/integration/checkout/fulfillment.md): Learn how to fulfill orders after a customer pays via checkout or payment links.
- [Define Your Checkout Experience](https://docs.withflex.com/developer-guides/integration/checkout/guides.md): Learn how to customize checkout sessions for common use cases like shipping, taxes, discounts, and embedded checkout.
- [How Checkout Works](https://docs.withflex.com/developer-guides/integration/checkout/how-checkout-works.md): Learn how to use checkout to collect HSA/FSA payments on your website.
- [Overview](https://docs.withflex.com/developer-guides/integration/checkout/off-session-checkouts-copied-1.md): Learn how session checkouts work.
- [Flex Checkout Quick Start](https://docs.withflex.com/developer-guides/integration/checkout/quick-start.md): Flex Checkout is our low-code integration to accept HSA/FSA payments.
- [Create A Payment Link](https://docs.withflex.com/developer-guides/integration/payment-links/create.md): Use the Flex Dashboard to create payment links and start accepting HSA/FSA payments without code.
- [Payment Links](https://docs.withflex.com/developer-guides/integration/payment-links/overview.md): Accept HSA/FSA payments without building a storefront.
- [Payouts & Balance Transactions API](https://docs.withflex.com/developer-guides/integration/payouts-balance-transactions.md): Track, filter, and reconcile money movements from Flex to your Shopify store
- [Reimbursement](https://docs.withflex.com/developer-guides/integration/reimbursement.md): Learn how to set up reimbursement integrations where consumers receive a Letter of Medical Necessity to file for reimbursement.
- [Integrating Flex with RevenueCat](https://docs.withflex.com/developer-guides/integration/revenuecat.md): Connect Flex with RevenueCat to sync subscription events, pass custom identifiers, and keep customer status up to date.
- [How Flex Shopify Payments Work](https://docs.withflex.com/developer-guides/integration/shopify/how-shopify-payments-app-works.md): Learn how the Flex Shopify payment app processes HSA/FSA payments and handles different cart eligibility scenarios.
- [Flex Shopify Payments App Installation](https://docs.withflex.com/developer-guides/integration/shopify/installation.md): Follow the steps below to set up your Flex account and configure your Shopify store.
- [Flex Shopify Payment App](https://docs.withflex.com/developer-guides/integration/shopify/overview.md): Flex provides a Shopify payment app to make it easy to accept HSA/FSA payments in your Shopify store checkout flow.
- [Shopify Product Templates](https://docs.withflex.com/developer-guides/integration/shopify/product-templates.md): Learn how to use Shopify product templates to control which products display the Flex HSA/FSA badge
- [Reconciliation](https://docs.withflex.com/developer-guides/integration/shopify/reconciliation.md): Understand money movement from Flex with your Shopify Store.
- [Shopify Subscriptions](https://docs.withflex.com/developer-guides/integration/shopify/shopify-subscriptions.md): How to add a reimbursement link for Shopify subscription purchases so customers can generate HSA/FSA documentation through Flex.
- [Shopify Test Store](https://docs.withflex.com/developer-guides/integration/shopify/shopify-test-store.md): Learn how to set up test payments and run test transactions on your Shopify store with Flex.
- [Custom Payment Methods Implementation](https://docs.withflex.com/developer-guides/integration/stripe/custom-payment-methods.md): Step-by-step guide for implementing Flex as a Stripe custom payment method with complete code examples.
- [Stripe Installation and Setup](https://docs.withflex.com/developer-guides/integration/stripe/installation.md): Set up Flex as a Stripe custom payment method in your application.
- [Stripe Custom Payment Methods Overview](https://docs.withflex.com/developer-guides/integration/stripe/overview.md): Learn how to integrate Flex as a Stripe custom payment method alongside traditional payment options.
- [Test Mode](https://docs.withflex.com/developer-guides/integration/test-mode.md): Flex's test mode allows you to test your integration without making real charges or payments.
- [How the Flex for WooCommerce Plugin Works](https://docs.withflex.com/developer-guides/integration/woocommerce/how-woocommerce-works.md): Learn how the Flex WooCommerce plugin processes HSA/FSA payments and handles different cart eligibility scenarios.
- [Flex for WooCommerce Installation](https://docs.withflex.com/developer-guides/integration/woocommerce/installation.md): Follow the steps below to set up your Flex account and configure your WooCommerce store.
- [Flex for WooCommerce](https://docs.withflex.com/developer-guides/integration/woocommerce/overview.md): Flex provides a WooCommerce plugin to make it easy to accept HSA/FSA payments in your WooCommerce store checkout flow.
- [Introduction](https://docs.withflex.com/developer-guides/introduction.md): Welcome to Flex! The easiest way to start accepting [HSA](https://www.healthcare.gov/glossary/health-savings-account-hsa/)/[FSA](https://www.healthcare.gov/glossary/flexible-spending-account-fsa/) Payments
- [Onboarding](https://docs.withflex.com/developer-guides/onboarding.md): We are thrilled to have you in our community.
- [API Product Creation Walkthrough](https://docs.withflex.com/developer-guides/products-and-prices/api-product-creation-walkthrough.md)
- [Get Started With Products and Prices](https://docs.withflex.com/developer-guides/products-and-prices/get-started-with-products-and-prices.md): Understand how to structure your business offerings for payments with Flex.
- [How Products and Prices Work](https://docs.withflex.com/developer-guides/products-and-prices/how-products-and-prices-work.md): Learn how products and prices function as core resources for your Flex integration.
- [Build a Subscription Integration](https://docs.withflex.com/developer-guides/subscriptions/getting-started.md): This guide describes how to sell a fixed-price monthly subscription offering using Flex.
- [Subscriptions](https://docs.withflex.com/developer-guides/subscriptions/overview.md): Learn how to create and manage recurring HSA/FSA payments through Flex.
- [Event Types](https://docs.withflex.com/developer-guides/webhooks/events.md): Learn about the different event types Flex sends to your webhook endpoint.
- [Legacy Webhooks Deprecation](https://docs.withflex.com/developer-guides/webhooks/legacy-webhooks.md): Migrate from legacy webhooks to our new webhook system by September 1, 2025.
- [Webhook Overview](https://docs.withflex.com/developer-guides/webhooks/overview.md): Listen to events at your webhook endpoint to automatically trigger reactions.
- [Using Redirects Instead of Webhooks](https://docs.withflex.com/developer-guides/webhooks/using-redirects.md): Learn how to handle checkout completion using redirects instead of webhooks for simpler implementation and testing
- [Verify Webhooks](https://docs.withflex.com/developer-guides/webhooks/verifying-webhooks.md): Learn how to securely verify webhook signatures to ensure they originate from Flex.
- [Disputes API Guide](https://docs.withflex.com/disputes-api-guide.md)
- [Early Fraud Warnings](https://docs.withflex.com/early-frau-warnings.md)
- [Welcome to Flex](https://docs.withflex.com/index.md): Accept HSA/FSA payments with ease
- [Marketing HSA/FSA](https://docs.withflex.com/merchant-success/introduction.md): Resources to help you succeed with Flex HSA/FSA payments
- [Brand & Messaging Hub](https://docs.withflex.com/merchant-success/marketing/brand-and-messaging-hub.md): Approved copy, compliance guidance, and brand assets, all in one place. Reference this page before publishing any HSA/FSA messaging across any channel.
- [Brand Guidelines](https://docs.withflex.com/merchant-success/marketing/brand-guidelines.md): Flex brand guidelines for merchants — logo usage, colors, typography, and co-branding rules.
- [Email & SMS](https://docs.withflex.com/merchant-success/marketing/email-and-sms.md): Templates and guidance for lifecycle marketers and CRM teams. Start here to announce HSA/FSA acceptance, add Flex to your flows, and drive conversion.
- [Launch Checklist](https://docs.withflex.com/merchant-success/marketing/launch-checklist.md): Your go-live plan. Follow these steps in order — no strategy needed, just execution.
- [Paid Media](https://docs.withflex.com/merchant-success/marketing/paid-media.md): This is the strategy and copy for performance marketers. Layer HSA/FSA messaging into your existing paid channels to drive conversion without increasing spend.
- [Results & Case Studies](https://docs.withflex.com/merchant-success/marketing/results-and-case-studies.md): Real results from Flex merchants across fitness, wellness, sleep, maternity, and more. Use these to build the case internally, set expectations, and see what's possible.
- [Social Media Templates](https://docs.withflex.com/merchant-success/marketing/social.md): Ready-to-use templates for announcing HSA/FSA payments on social media.
- [Social & Influencers](https://docs.withflex.com/merchant-success/marketing/social-and-influencers.md): Templates and guidance for social media managers and creator partnerships. Use these to announce HSA/FSA acceptance, build an evergreen social presence, and brief creators effectively.
- [Getting Started](https://docs.withflex.com/merchant-success/overview/getting-started.md): Learn how to maximize the value of HSA/FSA payments after implementation.
- [Highlight Flex at Checkout on Shopify](https://docs.withflex.com/merchant-success/overview/highlight-flex.md): Best practices for surfacing Flex higher in Shopify checkout using native payment customization.
- [Shopify Marketing App](https://docs.withflex.com/merchant-success/overview/shopify-marketing.md): Promote HSA/FSA eligibility on your Shopify store with the Flex Marketing App.
- [Customer Support FAQs](https://docs.withflex.com/merchant-success/support/customer-support.md): Common questions about HSA/FSA payments, Letters of Medical Necessity, and reimbursements.
- [Checkout & Inline Cart](https://docs.withflex.com/merchant-success/website/inline-cart.md): Display HSA/FSA eligibility messaging in your cart and checkout pages.
- [Landing Page](https://docs.withflex.com/merchant-success/website/landing-page.md): Create a dedicated HSA/FSA landing page to educate customers and drive conversions.
- [Product Detail Page (PDP)](https://docs.withflex.com/merchant-success/website/product-page.md): Add HSA/FSA eligibility badges to your product pages.

## OpenAPI Specs

- [openapi](https://docs.withflex.com/openapi.json)

## Optional

- [Status](https://status.withflex.com/)
- [Support](mailto:support@withflex.com)
- [Website](https://www.withflex.com)