HSA/FSA Mixed Cart Compliance: How Split Cart Handling Works for Ecommerce Merchants

An HSA/FSA mixed cart contains both eligible and non-eligible products in the same order.

For example, a customer may purchase:

• A blood pressure monitor
• An eligible supplement supported by a Letter of Medical Necessity (LMN)
• A cosmetic skincare product
• A branded water bottle

Some of these items may qualify as medical expenses under IRS guidelines, while others do not.

Mixed carts are common for ecommerce brands because many health catalogs include products that qualify alongside lifestyle or general health items. But as merchants expand their product offerings, mixed carts become increasingly difficult to avoid.

As per IRS rules, HSA and FSA funds can only be used to pay for qualified medical expenses. Qualified medical expenses are any products or services that can be used to treat, prevent, or mitigate a health condition. The implication of this rule is that every product in a transaction can’t automatically be charged to an HSA or FSA card.

Instead, eligibility must be determined at the individual item and customer level.

If non-eligible products are included in an HSA/FSA payment without proper eligibility validation and substantiation, the transaction may be declined. Or worse yet, your customer may run into penalties should they be audited by the IRS or their plan administrator.

In situations like these customers are left frustrated, and you may lose revenue from abandoned carts. Not to mention the brand impact if your customers are penalized.

Your main challenge then is creating an ecommerce HSA/FSA checkout that allows your customers to purchase everything they want while ensuring only eligible items are paid for with pre-tax funds.

The beauty of modern dedicated healthcare payment processors is that mixed carts payments now have a solution. HSA/FSA split card handling is the process of separating eligible and non-eligible products during checkout without adding friction for the consumer.

Rather than treating the order as one payment, a mixed HSA/FSA checkout creates two separate payment amounts. For example, when your customer gets to the checkout stage, they can choose to pay for their medically necessary supplement with their HSA/FSA card and then pay for their ineligible items with their credit card.

This HSA/FSA split card process allows your customers to complete a single order without manually creating multiple purchases.

Before payment begins, eligible products must be identified.

Product eligibility is typically determined using product databases like an Inventory Information Approval System (IIAS), or through a custom database through your payment provider. That's where dedicated HSA/FSA payment partners come in. Instead of requiring you to build IIAS infrastructure or determine eligibility per product, a partner like Truemed verifies eligibility at the product level within its own platform, determining which items in the cart qualify outright and which dual-use products need a Letter of Medical Necessity to substantiate the purchase.

The purpose of these eligibility databases is to ensure that only qualified purchases are submitted for HSA/FSA payment. Which in turn reduces unnecessary payment declines caused by incorrectly classified products.

Once eligibility has been confirmed, the checkout separates the order into eligible and non-eligible subtotals.

Your customer first pays the eligible subtotal with their HSA or FSA card and any remaining balance is then paid using another payment method.

If your customer's HSA or FSA account doesn’t have enough funds, they can also pay the balance of their eligible products with their debit or credit card. This approach allows your customers to complete the purchase without removing products from their cart.

HSA/FSA checkout compliance involves much more than separating payments.

To create a compliant checkout, you need to make sure that each eligible item is validated individually and supported by appropriate substantiation documents like Letters of Medical Necessity and itemized receipts.

Depending on your payment model, compliance may also involve Merchant Category Codes (MCCs) if you are a healthcare business like a doctor, optometrist etc., or an IIAS with Special Interest Group for IIAS Standards (SIGIS) participation if you don’t partner with a dedicated healthcare payment processor.

Managing these requirements internally can become complex, particularly as your product catalogs grow. Which is why it’s common for ecommerce brands to work with an HSA/FSA payment partner like Truemed* that automates eligibility verification, substantiation, and compliant payment workflows while reducing operational overhead.

*Truemed is for qualified customers. HSA/FSA tax savings vary. Learn more at truemed.com/disclosures.

Refunds become somewhat more complicated when orders contain multiple payment methods.

Card network rules require refunds to the original tender, and it protects your customer too: a cash refund, gift card, or store credit for an HSA purchase can create a taxable distribution they'd have to sort out with the IRS later.

The main reason being that it can cause tax reporting discrepancies for your customer and turn tax season into a nightmare. As a merchant, you’ll need to ensure that your refund policy explicitly states that refunds for HSA/FSA purchases can only be returned to the HSA/FSA account that was used.

If you charge shipping fees you will also need to refund the shipping fee to the HSA/FSA account that was used provided the products were HSA/FSA eligible.

Partial refunds for HSA/FSA purchases must also be returned to the HSA/FSA account and you’ll need to instruct your customer to keep the updated transaction records in case they’re audited.

Non-eligible products refunds on the other hand are handled as normal and returned to the traditional payment method used.

If you’re partnering with a dedicated payment processor you’ll need to ensure that they provide detailed documentation for each transaction including the date, products purchased, payment methods, order totals, and in the case of a refund, the refunded item and amount.

Maintaining detailed transaction records and issuing compliant receipts helps to simplify the refund process and supports audit readiness if the IRS has any questions.

You can reduce checkout friction by following these best practices:

• Clearly identify HSA/FSA eligible products throughout the shopping experience. A simple badge stating a product is eligible will do the trick.
• Make sure to display eligible and non-eligible subtotals before payment. This helps your customers see how much HSA/FSA funds they’ll need.
• Ensure that you keep detailed transaction and eligibility records.
• Always generate compliant receipts that support substantiation requirements as your customer may need them if they’re audited.
• Many customers don’t know much about their HSA/FSA accounts so make sure to educate them about how HSA/FSA payments work before they reach checkout.

Finally, you’ll want to partner with a payment processor that offers HSA/FSA split cart handling. At Truemed, we go beyond enabling a mixed HSA/FSA checkout by providing health intake surveys for LMNs, eligibility verification, and compliant payment workflows to help you remain compliant with IRS standards.

A well-designed HSA/FSA checkout does more than satisfy compliance requirements.

One of the main benefits of split cart handling is that it reduces payment failures by ensuring eligible and non-eligible products are processed correctly. The result is that your customers enjoy a smoother checkout experience and are less likely to abandon their purchase when payment options are clearly presented.

Supporting HSA/FSA payments can also unlock meaningful business growth. Customers paying with pre-tax healthcare dollars often have greater purchasing power,which often leads to higher AOV, without discounting your products. Instead of lowering prices, you can help eligible customers save an average of 30% through the tax advantages of HSA and FSA spending.

The opportunity isn’t insignificant either. Nearly half of Americans have access to an HSA or FSA, representing approximately $170 billion in healthcare assets. Reaching these shoppers broadens your customer base all while creating a better buying experience.