The custom device exemption's cap counts by type

A prosthetics or orthotics program that reads the custom device exemption as “we get five custom devices a year” has drawn the boundary in the wrong place. Section 520(b) of the Food, Drug, and Cosmetic Act, implemented at 21 CFR 812.3(b) — one of the seven categories on the UDI exemption's own named list — exempts a qualifying custom device from premarket review entirely: no 510(k), no PMA, no performance standard under section 514. But the exemption's volume limit doesn't cap a company's total output. It caps “five units per year of a particular device type,” and FDA's own guidance on the exemption spends most of its length on what “a particular device type” actually means. A program with three genuinely distinct custom device types isn't working from one five-unit allotment. It's working from three.

Five conditions, and all five have to hold

The statute sets five conditions together, not in the alternative. The device has to necessarily deviate from an otherwise applicable performance standard under section 514 or premarket approval requirement under section 515. It can't be generally available in finished form, for purchase or import, from a manufacturer, importer, or distributor. It can't be offered for commercial distribution through labeling or advertising. It has to be created or modified to treat a unique pathology or physiological condition that no other domestically available device addresses — originally read narrowly, for a single named patient identified in a physician's or dentist's order, until the 21st Century Cures Act broadened that prong in December 2016 to also cover a device built to meet the special needs of a physician's or dentist's own practice, certified in writing, without naming an individual patient for each unit produced. And no more than five units of that device type can be supplied in a year. A device that clears four of the five conditions and misses the fifth hasn't qualified for a smaller version of the exemption; it hasn't qualified at all.

What FDA reads as “a particular device type”

FDA's guidance interpreting the exemption, finalized in September 2014 after the FDA Safety and Innovation Act amended section 520(b) in 2012, doesn't leave “device type” to a manufacturer's own label for a product line. It sets out a multi-factor comparison — anatomical location, disease state, materials used, underlying technology, and indications for use — and treats two custom devices as the same type only where those factors substantially align. A spinal implant custom-shaped to one patient's anatomy and an upper-limb prosthetic custom-built for another aren't competing for the same five slots, even though both are supplied under the same company's custom device program in the same calendar year. Each distinct type carries its own five-unit ceiling, tracked separately.

The count is patients, not shipments

The guidance also narrows what actually gets counted toward the five. FDA counts new custom devices — in practice, new patients for a patient-specific device, or new physician certifications for a practice-specific one — not every unit that leaves the building. A replacement made for a patient who already received one of the year's five, where the original is returned to the manufacturer or destroyed, doesn't add a sixth count against the same type. A file that tallies every unit shipped, replacements included, is enforcing a stricter limit than the one FDA actually applies — and a file that ignores the distinction between device types is enforcing a limit far looser than the one that actually applies.

The exemption comes with its own reporting duty

Qualifying for the exemption doesn't end a manufacturer's obligations to FDA. A firm that supplies any custom device during a calendar year owes FDA an annual report identifying the device types supplied and the quantity of each — the same record FDA's guidance describes checking against a manufacturer's own five-unit accounting. A custom device program with no process for compiling that report before FDA asks for it is already behind on a duty the exemption itself created, not one bolted on afterward.

Not a narrower 510(k) — a different door entirely

A Special 510(k) is still premarket review, narrowed to a manufacturer's own already-cleared device. The custom device exemption isn't a narrower version of that review; it's the absence of it, available only while the device stays inside all five conditions. A device that starts as a custom device and later gets marketed more broadly, or crosses the five-unit count for its type, has left the exemption's terms and needs the 510(k) or PMA clearance any other device of its kind would need — the custom device history doesn't carry over as credit toward that review.

Where this meets the file

A custom device tracking file built around this exemption needs a row per device type, not per company, with the anatomical-location-and-technology factors that define the type recorded alongside the running annual count and the report due date those counts feed. A custom device exemption worksheet built around FDA's own five-factor device-type test is previewed in the launch catalog. If your program defines device type differently, the shelf takes that correction directly.