Flex Alternatives for Merchants Offering HSA/FSA
Flex requires a checkout integration. Compare merchant alternatives on setup time, pricing, and recurring billing, including one that needs no engineering.
6 minute read
TLDR;
Flex (withflex.com) lets merchants accept HSA/FSA cards by integrating Flex's checkout into their store. If you've looked at Flex and hesitated, it's usually for one of three reasons: it's an engineering project, it's built for online checkout, and the terms come through a sales process. The alternative built for owners who just want FSA/HSA today is Burst: self-serve signup, running in about 30 minutes, no integration, $100 a month with no contract and never a percentage of your revenue, and it works for brick-and-mortar and recurring billing just as well as e-commerce.
(Shopping as a consumer, not a merchant? You can get a letter for any purchase directly from Burst.)
Flex alternatives for merchants at a glance
Offering | Getting live | Cost to you | Built for | Recurring billing |
|---|---|---|---|---|
Flex | Sales call, then checkout integration, typically weeks | Not public; typically a rev share | Online brands in their partner network | Limited support |
Truemed | Sales call, then checkout integration, typically weeks | Not public; typically a rev share | Online brands in their partner network | Limited support |
Burst | Self-serve, live in 30 minutes, no integration | $100/month, month to month, no contract, no revenue share | Every business: retail, gyms, spas, studios, online or in person | Works with your existing billing; no card rails involved |
Why merchants go looking for a Flex alternative
Flex is genuinely payments infrastructure, and that's both its pitch and its cost. Offering it means integrating their checkout into your stack, running your customers' purchases across their card rails with real-time substantiation, and for subscriptions, their documentation says eligibility is re-validated at every renewal. That's an engineering commitment with a sales process in front of it, and it presumes your revenue flows through an online checkout at all. A front-desk gym, a med spa, a studio with its own billing system: none of them fit that shape. And their merchant terms aren't published, so you can't even price the decision without entering the pipeline.
Burst: no integration, live in 30 minutes
Burst takes the opposite approach: it never touches your checkout, which is exactly why any business can offer it. Signup is self-serve; partners are live in 30 minutes. Your customers keep paying you the way they already do, on any card and any billing system. Burst covers the Letter of Medical Necessity side: a licensed clinician reviews each member's case, the letter arrives within 24 hours of approval, and Burst files the reimbursement claim; the member's plan administrator pays the reimbursement out of their FSA, HSA, or HRA to them.
Pricing is public and flat: $100 a month, month to month, no contract, and never a percentage of your revenue. Members pay a $20 one-time letter fee, or you cover it for them. If a clinician doesn't approve a letter or a claim is denied, the fee refunds automatically, so recommending Burst never costs your customer anything. Neither Flex nor Truemed advertises a comparable guarantee.
See how it works or go live now.
Truemed
Truemed is functionally the same product as Flex: card rails at partner checkouts, an LMN service, a marketplace of partner brands, a sales call to learn your terms (typically a rev share), and an integration to go live. Swapping Flex for Truemed swaps the logo, not the model. The Truemed vs Flex comparison breaks that down.
The recurring billing problem
Memberships are where HSA/FSA spend matters most to gyms, spas, and studios, and card rails handle them worst. IRS rules (the IIAS framework, Notices 2006-69 and 2007-2) require real-time substantiation of HSA/FSA card payments, so a recurring card charge needs a fresh check at every renewal. Flex built machinery for that inside its network; it's still machinery your revenue depends on. Burst skips the problem: members pay through your existing billing on their normal card, and the letter covers the expense. Nothing changes in your billing at all.
How to choose
You're an online brand that wants HSA/FSA cards accepted in the checkout itself, and you have the engineering capacity and team bandwith: that's the case Flex was built for.
You want the benefit live today, for every kind of customer, at a published price, with zero engineering: only Burst does that.
You run recurring billing: card-rail models are structurally the wrong tool. Start with the one that's built for subscriptions.
Frequently asked questions
What does Flex cost a merchant?
Flex doesn't publish merchant pricing; terms come through their sales process (typically a rev share %). Burst's pricing is public: $100 a month, month to month, no contract, no percentage of revenue.
Does offering Burst require integrating anything?
No. There is no technical integration and your checkout stays untouched. That's also why Burst works for in-person businesses, not just online stores.
Can my brick-and-mortar business offer Flex?
Flex is built around online checkout integration. If your revenue happens in person or through your own billing system, you're outside the model. Burst works the same for online, in-person, and hybrid businesses.
What happens if my customer's claim is denied?
With Burst, the letter fee refunds automatically if a clinician doesn't approve the letter or the plan denies the claim. Flex and Truemed don't advertise a comparable guarantee.
Can members get letters for past purchases?
No. IRS rules require the letter to be dated on or before the purchase. That binds Burst, Flex, Truemed, and every other provider equally.
Related guides
Offer HSA/FSA savings this week
Self-serve setup in about 30 minutes. $100 a month, no contract, no revenue share, no integration. Get started with Burst or see how it works.
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