Millions of Medicare beneficiaries who rely on walkers, home oxygen systems, hospital beds, and other prescribed equipment face a cost-sharing formula that has not changed in decades: Medicare pays 80% of the approved amount, and the patient covers the remaining 20% after meeting the annual Part B deductible. That split, written directly into federal law under Section 1834 of the Social Security Act, determines what seniors actually pay out of pocket for the equipment their doctors order for home use. But whether patients land on the favorable side of that formula depends on a variable most people overlook: whether their supplier accepts Medicare assignment.
How the 80/20 Split Works for Home Equipment
The math behind Medicare’s coverage of durable medical equipment starts with a single statutory rule. For covered items, payment equals 80% of the payment basis, with the beneficiary responsible for the other 20%. That payment basis is not the sticker price a supplier might advertise. Under the statute in Section 1834, the Medicare-allowed amount is tied to fee schedule limits and subject to the annual Part B deductible. According to CMS payment policy, Medicare generally pays 80% of the allowed charge after subtracting any unmet deductible, and the beneficiary owes the remaining 20% plus whatever portion of the deductible has not yet been satisfied.
This structure applies across the full range of home medical equipment that Part B covers: standard and wheeled walkers, portable and stationary oxygen concentrators, continuous positive airway pressure (CPAP) devices, manual wheelchairs, and hospital beds. The program’s rules for durable medical equipment define which items qualify, how long they are rented or owned, and when replacement or maintenance is allowed. For many products, Medicare treats the equipment as a capped rental, paying monthly over a set period while the beneficiary continues to pay coinsurance on each claim.
The actual dollar amounts start with the DMEPOS fee schedule, which sets maximum payment limits by HCPCS billing code and geographic area. CMS publishes these values in its DMEPOS fee schedule, and suppliers may not bill Medicare more than the allowed charge for an assigned claim. When a supplier accepts assignment, the supplier agrees to charge no more than the Medicare-approved amount, and the beneficiary’s exposure is capped at 20% of that figure once the deductible is met. The distinction matters because suppliers that do not accept assignment can bill above the approved amount, shifting costs beyond the standard 20% share onto the patient.
Supplier Assignment Gaps and Hidden Costs
The 80/20 formula assumes a cooperative arrangement between Medicare and the equipment supplier. In practice, the beneficiary’s actual bill hinges on whether the supplier participates in assignment. A supplier that declines assignment can charge more than the Medicare-approved amount for most items, and the patient absorbs that excess on top of the standard coinsurance and any remaining deductible. For high-use categories like home oxygen, where equipment is rented monthly and supplies are reordered regularly, even a modest markup compounds over time and can significantly raise annual out-of-pocket spending.
Public data from the CMS DMEPOS provider summary portal tracks utilization and spending patterns by supplier and geography, but it does not pre-calculate how often suppliers in a given county decline assignment or how that refusal translates into added beneficiary liability. The fee schedule files published by CMS list approved amounts by HCPCS code for specific items, yet connecting those prices to real out-of-pocket costs requires knowing the supplier’s participation status and the beneficiary’s progress toward the Part B deductible. That information gap means the standard “you pay 20%” message on Medicare.gov can understate what patients actually spend, particularly in areas with fewer participating suppliers or limited competition.
Beneficiaries can search for participating suppliers through the Medicare supplier directory, but no single public tool cross-references supplier assignment rates with local claim volume to flag counties where patients face above-average exposure. The result is a blind spot: the statutory 80/20 split is clear, but the real-world cost to patients varies by ZIP code in ways that existing federal data tools do not fully capture. Seniors in rural regions or smaller markets may have little choice but to use a non-assignment supplier if no alternative is available within a reasonable distance, leaving them vulnerable to higher charges.
What Patients Can Do Now
For individual beneficiaries, the most effective step is to ask a prospective supplier upfront whether it accepts Medicare assignment for the specific item being ordered. If the answer is no, patients can request a written estimate that shows the Medicare-approved amount, the expected coinsurance, and any additional balance billing. Comparing that estimate with quotes from other local suppliers can reveal significant differences in total cost, even when the underlying fee schedule amount is identical.
Clinicians and discharge planners also play a role. When arranging home equipment for a patient leaving the hospital or clinic, steering prescriptions toward suppliers that accept assignment can help protect patients from unexpected bills. Policymakers, meanwhile, face a separate challenge: without clearer public reporting on assignment rates and beneficiary liability by region, it remains difficult to target oversight or education efforts to the communities where the 80/20 promise is least likely to match what patients actually pay.
