For Business

For Shoppers

For Business

For Shoppers

Make HSA/FSA payments your next revenue driver

Increase AOV by 50% and checkout conversion by 30% with the only HSA/FSA payments infrastructure built for top health and wellness brands.

Maximize Your Checkout

Flex Supply Co.

HSA/FSA Revenue

+30.5%

$1,250,000

Trending up this month

Average Order Value

+45%

$358.00

AOV growth is on track

Conversion Rate

+12.5%

85%

Steady performance increase

Net Revenue

Total for the last 3 months

Jan 1

Jan 15

Feb 1

Feb 15

Mar 1

Mar 15

AOV

Total for the last 3 months

Jan 1

Jan 15

Feb 1

Feb 15

Mar 1

Mar 15

Top Products

Total for the last 3 months

Fitness Equipment

4,103

Skincare

2,539

Eye Glasses

1,258

Footwear

950

Top Customers

Total for the last 3 months

Sam O’Keefe

10

Miguel Toledo

9

Connor Olsen

8

Nick Holland

6

Test Mode

Transform checkout. Drive more revenue.

Transform checkout. Drive more revenue.

See what leading brands achieve by accepting HSA/FSA payments with Flex:

See what leading brands achieve by accepting HSA/FSA payments with Flex:

CONVERSION LIFT

+30%

More shoppers complete checkout with HSA/FSA

CONVERSION LIFT

+30%

More shoppers complete checkout with HSA/FSA

HIGHER AOV

+50%

Customers spend more using health benefit funds

HIGHER AOV

+50%

Customers spend more using health benefit funds

FEWER RETURNS

-10%

Fewer returns when buyers use pre-tax dollars

FEWER RETURNS

-10%

Fewer returns when buyers use pre-tax dollars

REPEAT BUYERS

92%

Of customers said they'll return because of HSA/FSA

REPEAT BUYERS

92%

Of customers said they'll return because of HSA/FSA

Your all-in-one HSA/FSA payments infrastructure

Your all-in-one HSA/FSA payments infrastructure

Everything you need to accept HSA and FSA payments and support complex enterprise operations at scale.

Everything you need to accept HSA and FSA payments and support complex enterprise operations at scale.

Effortless HSA/FSA Payments

Enable seamless HSA/FSA payments in-app or on your website. We handle the complexity of auto-substantiation, split cards, subscriptions, and more.

Built-in Compliance

Flex helps manage HSA/FSA eligibility before and after purchase and supports physician-reviewed Letters of Medical Necessity when required.

Smarter Insights

Access powerful HSA/FSA focused dashboards and insights to identify your customers’ spending trends and generate more revenue.

Flexible integration for modern e-commerce

curl --request POST \

--url https://api.withflex.com/v1/checkout/sessions \

--header 'Authorization: Bearer ' \

--header 'Content-Type: application/json' \

--data '{

"checkout_session": {

"allow_promotion_codes": true,

"line_items": [

{

"price": "",

"price_data": {

"description": "",

"product": "",

"unit_amount": 1,

"recurring": {

"interval": "daily",

"interval_count": 1,

"trial_period_days": 1

},

"metadata": {}

},

"quantity": 123,


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API-first and fully customizable

Flex integrates seamlessly with your tech stack. From custom checkouts to Shopify, our HSA/FSA payments infrastructure adapts to how you sell.

Speak with a Specialist

Built for enterprise scale

Support complex business models, including subscriptions, high-volume transactions, and recurring payments. Flex is designed for the demands of large brands.

Fast, reliable implementation

Get up and running quickly with clear documentation, dedicated support, and proven reliability—even during peak sales periods.

Explore How Flex Fits Your Tech Stack

Integrates with any
checkout or payment system

  • Shopify
  • WooCommerce
  • RevenueCat
  • Kintsugi
  • Shopline

Flexible integration for modern e-commerce

curl --request POST \

--url https://api.withflex.com/v1/checkout/sessions \

--header 'Authorization: Bearer ' \

--header 'Content-Type: application/json' \

--data '{

"checkout_session": {

"allow_promotion_codes": true,

"line_items": [

{

"price": "",

"price_data": {

"description": "",

"product": "",

"unit_amount": 1,

"recurring": {

"interval": "daily",

"interval_count": 1,

"trial_period_days": 1

},

"metadata": {}

},

"quantity": 123,


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5

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10

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13

14

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16

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19

20

21

22

API-first and fully customizable

Flex integrates seamlessly with your tech stack. From custom checkouts to Shopify, our HSA/FSA payments infrastructure adapts to how you sell.

Speak with a Specialist

Built for enterprise scale

Support complex business models, including subscriptions, high-volume transactions, and recurring payments. Flex is designed for the demands of large brands.

Fast, reliable implementation

Get up and running quickly with clear documentation, dedicated support, and proven reliability—even during peak sales periods.

Explore How Flex Fits Your Tech Stack

Integrates with any
checkout or payment system

  • Shopify
  • WooCommerce
  • RevenueCat
  • Kintsugi
  • Shopline

Flexible integration for modern e-commerce

curl --request POST \

--url https://api.withflex.com/v1/checkout/sessions \

--header 'Authorization: Bearer ' \

--header 'Content-Type: application/json' \

--data '{

"checkout_session": {

"allow_promotion_codes": true,

"line_items": [

{

"price": "",

"price_data": {

"description": "",

"product": "",

"unit_amount": 1,

"recurring": {

"interval": "daily",

"interval_count": 1,

"trial_period_days": 1

},

"metadata": {}

},

"quantity": 123,


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2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

API-first and fully customizable

Flex integrates seamlessly with your tech stack. From custom checkouts to Shopify, our HSA/FSA payments infrastructure adapts to how you sell.

Speak with a Specialist

Built for enterprise scale

Support complex business models, including subscriptions, high-volume transactions, and recurring payments. Flex is designed for the demands of large brands.

Fast, reliable implementation

Get up and running quickly with clear documentation, dedicated support, and proven reliability—even during peak sales periods.

Explore How Flex Fits Your Tech Stack

Integrates with any
checkout or payment system

  • Shopify
  • WooCommerce
  • RevenueCat
  • Kintsugi
  • Shopline

Flexible integration for modern e-commerce

curl --request POST \

--url https://api.withflex.com/v1/checkout/sessions \

--header 'Authorization: Bearer ' \

--header 'Content-Type: application/json' \

--data '{

"checkout_session": {

"allow_promotion_codes": true,

"line_items": [

{

"price": "",

"price_data": {

"description": "",

"product": "",

"unit_amount": 1,

"recurring": {

"interval": "daily",

"interval_count": 1,

"trial_period_days": 1

},

"metadata": {}

},

"quantity": 123,


1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

API-first and fully customizable

Flex integrates seamlessly with your tech stack. From custom checkouts to Shopify, our HSA/FSA payments infrastructure adapts to how you sell.

Speak with a Specialist

Built for enterprise scale

Support complex business models, including subscriptions, high-volume transactions, and recurring payments. Flex is designed for the demands of large brands.

Fast, reliable implementation

Get up and running quickly with clear documentation, dedicated support, and proven reliability—even during peak sales periods.

Explore How Flex Fits Your Tech Stack

Integrates with any
checkout or payment system

  • Shopify
  • WooCommerce
  • RevenueCat
  • Kintsugi
  • Shopline

Flexible integration for modern e-commerce

curl --request POST \

--url https://api.withflex.com/v1/checkout/sessions \

--header 'Authorization: Bearer ' \

--header 'Content-Type: application/json' \

--data '{

"checkout_session": {

"allow_promotion_codes": true,

"line_items": [

{

"price": "",

"price_data": {

"description": "",

"product": "",

"unit_amount": 1,

"recurring": {

"interval": "daily",

"interval_count": 1,

"trial_period_days": 1

},

"metadata": {}

},

"quantity": 123,


1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

API-first and fully customizable

Flex integrates seamlessly with your tech stack. From custom checkouts to Shopify, our HSA/FSA payments infrastructure adapts to how you sell.

Speak with a Specialist

Built for enterprise scale

Support complex business models, including subscriptions, high-volume transactions, and recurring payments. Flex is designed for the demands of large brands.

Fast, reliable implementation

Get up and running quickly with clear documentation, dedicated support, and proven reliability—even during peak sales periods.

Explore How Flex Fits Your Tech Stack

Integrates with any
checkout or payment system

  • Shopify
  • WooCommerce
  • RevenueCat
  • Kintsugi
  • Shopline

Why brands bet on Flex

We chose Flex because it offers the most comprehensive solution for enabling HSA/FSA payments.

Lisa Thorson

Director Regulatory Affairs

Our partnership with Flex helps make holistic wellness more accessible to everyone.

Natasha Trindall

General Manager

Flex empowers our customers to invest in fitness using their HSA/FSA funds.

Michael Maas

Chief Sales Officer

Flex improved our conversion rate and added trust at checkout.

Raechelle Hoki

VP of Marketing

Flex helps make cutting-edge fitness more affordable and accessible.

Ulrich Dempfle

Co-founder

Flex helps make cutting-edge fitness more affordable and accessible.

Forrest Smith

CEO and Co-founder

Why brands bet on Flex

We chose Flex because it offers the most comprehensive solution for enabling HSA/FSA payments.

Lisa Thorson

Director Regulatory Affairs

Our partnership with Flex helps make holistic wellness more accessible to everyone.

Natasha Trindall

General Manager

Flex empowers our customers to invest in fitness using their HSA/FSA funds.

Michael Maas

Chief Sales Officer

Flex improved our conversion rate and added trust at checkout.

Raechelle Hoki

VP of Marketing

Flex helps make cutting-edge fitness more affordable and accessible.

Ulrich Dempfle

Co-founder

Flex helps make cutting-edge fitness more affordable and accessible.

Forrest Smith

CEO and Co-founder

Why brands bet on Flex

Why brands bet on Flex

We chose Flex because it offers the most comprehensive solution for enabling HSA/FSA payments.

Lisa Thorson

Director Regulatory Affairs

Our partnership with Flex helps make holistic wellness more accessible to everyone.

Natasha Trindall

General Manager

Flex empowers our customers to invest in fitness using their HSA/FSA funds.

Michael Maas

Chief Sales Officer

Flex improved our conversion rate and added trust at checkout.

Raechelle Hoki

VP of Marketing

Flex helps make cutting-edge fitness more affordable and accessible.

Ulrich Dempfle

Co-founder

Flex helps make cutting-edge fitness more affordable and accessible.

Forrest Smith

CEO and Co-founder

We chose Flex because it offers the most comprehensive solution for enabling HSA/FSA payments.

Lisa Thorson

Director Regulatory Affairs

Our partnership with Flex helps make holistic wellness more accessible to everyone.

Natasha Trindall

General Manager

Flex empowers our customers to invest in fitness using their HSA/FSA funds.

Michael Maas

Chief Sales Officer

Flex improved our conversion rate and added trust at checkout.

Raechelle Hoki

VP of Marketing

Flex helps make cutting-edge fitness more affordable and accessible.

Ulrich Dempfle

Co-founder

Flex helps make cutting-edge fitness more affordable and accessible.

Forrest Smith

CEO and Co-founder

Flexible at scale, precise by design across industries

Flex takes care of the details so you can get set up to accept HSA/FSA payments quickly and compliantly, with personalized support to meet your enterprise needs.

Flex takes care of the details so you can get set up to accept HSA/FSA payments quickly and compliantly, with personalized support to meet your enterprise needs.

Fitness
Sleep
Home
Skincare
Supplements
Footwear

Flex HSA/FSA payments FAQs

Flex HSA/FSA payments FAQs

Find answers about accepting HSA and FSA payments, and how Flex helps grow your business.

Find answers about accepting HSA and FSA payments, and how Flex helps grow your business.

How does HSA and FSA payment processing work?

An HSA and FSA payment processing tool like Flex helps businesses accept HSA/FSA payments while handling eligibility and compliance requirements during checkout.

When a customer selects Flex as a payment option, Flex confirms whether the purchase is eligible based on applicable guidelines. If additional documentation is required, the customer may be guided through a telehealth consultation to determine eligibility. Once complete, the customer enters their HSA/FSA card details just like they would with a credit card, and Flex processes the payment.

Flex adheres to IRS eligibility guidelines and applicable compliance requirements to support HSA/FSA transactions at checkout. Flex works with your team to review product eligibility and integrate HSA/FSA payments into your existing checkout flow.

Is the process to accept HSA & FSA card payments the same as other payment methods?

For businesses, accepting HSA and FSA payments involves additional eligibility and compliance considerations compared to standard payment methods. Flex manages these requirements with ease, enabling your team to handle eligibility and compliance at scale.

For customers, the experience is similar to other payment methods once Flex is enabled. At checkout, the customer selects Flex and enters their HSA or FSA card details just like they would with a credit or debit card. If needed, Flex may guide the customer through a telehealth consultation during checkout to help determine purchase eligibility before completing the payment.

Is my business eligible to accept HSA & FSA payments?

Flex can help you through the process of determining whether your business is eligible to accept HSA and FSA payments based on IRS guidelines. Once you connect with our team, we can review your product offerings and identify which items you sell are always eligible and which may be considered dual-purpose.

If you have eligible products, Flex can also support the integration of HSA/FSA payment acceptance into your existing checkout experience. Flex works with both custom-built checkouts and supported platforms, allowing teams to enable HSA/FSA payments without disrupting their current payment flow.

Do Flex HSA/FSA payments adhere to the IRS guidelines?

Yes, Flex’s HSA/FSA infrastructure adheres to the IRS guidelines.

Do I need a different tool to provide Letters of Medical Necessity to my customers at checkout?

No. Flex includes support for Letters of Medical Necessity, so you do not need a separate tool at checkout.

When a Letter of Medical Necessity is required for a purchase, Flex prompts a brief, chat-based telehealth consultation as part of the checkout flow. The customer completes the consultation, and a licensed healthcare practitioner reviews the information to determine eligibility. If approved, the customer receives their Letter of Medical Necessity.

Flex handles the consultation workflow and documentation delivery, so businesses do not need to source, integrate, or manage an additional solution.

What if my customer wants to split their purchase between their HSA/FSA card and a credit or debit card?

Yes. With Flex, customers can split a purchase between their HSA or FSA card and a standard credit or debit card.

During checkout, the customer can choose how much of the purchase to apply to their HSA or FSA card and place the remaining balance on their credit or debit card. This allows customers to complete purchases even when their HSA or FSA balance does not cover the full amount, helping reduce checkout friction and support completed transactions.

Can Flex HSA/FSA payments handle subscriptions and memberships?

Flex is set up to handle a wide range of subscription models, empowering you to offer your customers more options that suit their preferences, all while driving even more recurring revenue.

Does the Flex HSA/FSA checkout integration work with coupons and promotions?

Yes. Flex’s checkout integration supports coupons and promotional codes, allowing businesses to apply existing discount strategies without changing their checkout flow.

Promotions and discounts work alongside Flex payments, so teams can continue to run standard campaigns, measure performance, and maintain consistency across payment methods. This allows Flex to fit into existing marketing and revenue operations without requiring separate tooling or workflows.

Does Flex integrate with any ecommerce website?

Flex integrates into your existing ecommerce technology stack and works with both custom-built checkouts and leading ecommerce platforms.

Businesses can integrate Flex directly into a custom checkout experience, or use one of Flex’s supported platform integrations, including Shopify, WooCommerce, Shopline, RevenueCat, and others. This flexibility allows teams to adopt Flex without restructuring your current checkout architecture.

Does Flex offer an API for integrating HSA/FSA payments into my checkout?

Yes. Flex is built API-first and provides APIs that allow businesses to integrate HSA/FSA payments into their checkout experience.

Using the Flex API, businesses can create checkout sessions, redirect customers to complete their purchase, and listen for checkout events through webhooks to support order fulfillment and downstream workflows. This approach allows teams to integrate Flex into custom checkout flows and existing systems without changing their core architecture.

Flex’s developer documentation includes detailed guides and API references that walk through session creation, webhook configuration, and supported checkout events, helping engineering teams implement Flex in a way that fits their technical requirements.

How do I get started accepting HSA/FSA payments?

To get started, reach out to a Flex expert.

Flex works with your team to help you skip manual and costly steps to becoming eligible to accept HSA and FSA payments. Our team assists with product eligibility, compliance considerations, and implementation, so you can get ready to offer HSA/FSA payments with confidence.

Once you connect with Flex, we’ll guide you through the setup process and support your team as you integrate Flex into your checkout.

Latest insights for HSA/FSA-eligible brands

SPEAK WITH A FLEX EXPERT TO

Start accepting HSA/FSA
payments to drive more revenue

Identify if you need payments or reimbursements

See how Flex looks in your checkout flow

Easily integrate Flex with no changes to your stack

Book a Demo