Trunk stock inventory for medical device reps: bill-only leakage, expired implants, the 2026 ASC shift and what a count looks like done right.
Add up the implants, instruments and disposables in the trunks of a 75-rep sales force and you get a warehouse. It has no address, no shelf labels and no cycle count. Finance carries it on the balance sheet at cost. Commercial ops knows roughly what is in it. The rep knows exactly, until a case runs long and a tray gets left in an OR.
This guide covers trunk stock inventory for medical device companies in the US: why it is invisible, where the money leaks (bill-only, unbilled consumption, expired implants), why the shift of procedures to ambulatory surgery centers (ASCs) in 2026 makes it urgent, what a trunk stock count looks like done right, and how finance and commercial ops split the work.
Trunk stock: the invisible warehouse
Trunk stock is inventory assigned to a rep and carried in a vehicle or a home office so that it is available for cases without a hospital order. For orthopedics, spine, cardiovascular and surgical robotics it is the fastest way to serve a surgeon. It is also the stock the ERP sees least. The ERP records a transfer to a rep location and then goes quiet. Consumption, swaps between reps, loaners passed hand to hand at a hospital parking lot: none of that gets back into the system until someone reconciles.
The MedTech Inventory Visibility Gap Report 2025, a Ventory survey of 150+ field inventory leaders across North America, EMEA and APAC, puts a number on the quiet. 68% of field teams confirm inventory availability before a case by call, text or spreadsheet. Only 22% say they are very or completely confident their inventory data is accurate at any given moment. 28% still rely on a physical count or trunk check, and only 11% see their data update in real time.
Bill-only and unbilled consumption
Bill-only is the purchase order a hospital raises after the case, for the implant the rep brought in from the trunk. It is the standard model for trunk stock. It is also where revenue leaks. The rep writes the lot numbers on a sticker sheet or an implant log, the sheet goes to customer service, and the invoice follows days or weeks later. Every step is a chance to lose a lot, a size or a whole implant.
In the Gap Report, 86% of respondents experience billing delays due to inventory issues at least quarterly; 31% monthly and 16% weekly. The report's modeled cost leakage for a 75-rep team puts unbilled or delayed revenue capture at $250,000 to $500,000 a year, with the full range across expiry, emergency freight, unbilled revenue and rep time at $750,000 to $1.55 million. Those are modeled estimates, and the report says so. The pattern they describe is not: consumption that is recorded on paper gets billed late, and some of it never gets billed at all.
Expired implants in cars
Implants have expiry dates. Trunks have no FEFO logic. A size 4 that nobody needed for eight months is still in the bin when it expires, and the rep finds out when the scanner in the OR rejects it, or worse, when it is already on the back table. In the Gap Report 75% of respondents cite expiry as a meaningful cost, and 20-30% of field inventory is reported as slow-moving or expired. A trunk is the worst place for an expiring implant: high value, low velocity, no alerts.
Expiry management for trunk stock means three things. Lot and expiry recorded per unit at the moment it is assigned to the rep. An alert at 90, 60 and 30 days that goes to the rep and to commercial ops. A swap routine that moves a short-dated unit from a slow trunk to a fast one before it expires, not after. See the product expiry management use case for how that works in practice.
The ASC shift changes the math in 2026
Trunk stock was built for hospitals. The 2026 Medicare payment rules push more procedures out of them. In the CY 2026 OPPS and ASC final rule published 21 November 2025, CMS added 289 procedures to the ASC Covered Procedures List, plus 271 codes that were removed from the inpatient-only list, and started a three-year phase-out of the inpatient-only list with the removal of 285 mostly musculoskeletal procedures for 2026. Becker's Spine Review counts 168 orthopedic codes among the additions, including revision total hip and total knee arthroplasty and posterior lumbar interbody fusion (CPT 22630 and 22633).
For a rep that means more cases at more sites, and ASCs do not hold consignment the way a large hospital does. They expect the rep to bring the set. More sites served from the same trunk means more swaps, more bill-only paperwork and more chances to carry the wrong size to the wrong building. The trunk has to be counted like a warehouse because it is now serving like one.
What a trunk stock count looks like done right
A trunk stock count is not a quarterly audit day. It is a continuous process with five parts.
- Scan, do not type. Every unit assigned to a rep is scanned in by UDI, with lot and expiry read from the barcode. Every consumption is scanned at the point of care, in the OR or the ASC. The scan is the record; the implant log becomes a report, not an input.
- Par levels per rep. Each trunk has a target quantity per SKU, set from case mix and lead time, not from what the rep asked for in 2023. The system shows the gap between par and actual every day.
- Replenishment triggers. A consumption scan below par raises a replenishment request to the distribution center. No email, no Friday batch.
- Expiry alerts. 90, 60 and 30 days before expiry, with a suggested swap to a trunk that will use the unit. Short-dated units move toward demand.
- Lot per rep, always. Every lot is assigned to a named rep and a location. A recall query returns the list of trunks and hospitals holding that lot in minutes.
The count itself becomes a cycle count: a short scan of one bin or one category per week, prompted by the app, reconciled against the system. Full physical counts drop to once a year, and the variance drops with them. The technology that makes this work is ordinary: a phone, a barcode scanner, an app that works offline in a parking garage and syncs to SAP, Microsoft Dynamics, Oracle or NetSuite when it finds a signal.
At a glance: four ways companies manage trunk stock
The right approach depends on rep count, implant value and how many sites each rep serves. The table judges each option on the same criteria.
| Approach | Who owns the count | Lot and expiry per unit | Bill-only capture | ERP sync | Best for |
|---|---|---|---|---|---|
| Spreadsheet, texts and implant logs | The rep | On paper, if the rep writes it down | Days to weeks, manual re-keying | None | Under 20 reps, low implant value, single region |
| ERP only (SAP, Dynamics, Oracle) | Finance, at the transfer | At goods issue; lost once the unit is in the trunk | Via customer service, after the fact | Native, but blind past the rep location | Companies with mostly consigned or hospital-held stock and little in trunks |
| Distributor or 3PL managed | The distributor | Yes, inside the distributor's system | Handled by the distributor, visibility depends on the contract | To the distributor's systems | Manufacturers that outsource the field entirely and accept the margin |
| Field inventory layer (Ventory and similar) | Commercial ops, shared with the rep and finance | Yes, scanned per unit, per rep, per location | Scan at the point of care is the billing trigger | Two-way, ERP stays the system of record | 20+ reps, implants with expiry, bill-only revenue that matters |
Judged honestly, the spreadsheet is free and works for a small team with disciplined reps. The ERP-only route is the cheapest on paper and the most expensive in unbilled revenue. A distributor removes the problem from your books and takes margin for it. A field inventory layer costs a subscription and 4-8 weeks of implementation and is the only option that gives you your own count at the rep level.
How finance and commercial ops split the work
Trunk stock fails when it belongs to everyone. The split that works:
- Finance owns the value. Inventory on the balance sheet, reserve for obsolescence, write-off policy for expired units, and the variance between system and count. Finance sets the tolerance (for example, 1% of value per quarter) and reviews it monthly.
- Commercial ops owns the count. Par levels per rep, cycle count cadence, replenishment rules, expiry swaps, and the recall process. Commercial ops reports variance against finance's tolerance and fixes root causes.
- The rep owns the scan. Scan in, scan out, scan at the point of care. Nothing else. A rep's compensation should never depend on filling in a spreadsheet correctly.
- Customer service owns bill-only turnaround. Time from consumption scan to invoice, measured in days. The target is under 5 business days; the scan makes it possible.
One shared dashboard, four owners, one system of record. The ERP keeps the value. The field inventory layer keeps the count. For a worked example of the costs, run your own numbers through the Consigned Stock P&L calculator, then check fit in three minutes with the Ventory Fit Check. The whitepaper Loaner Kits and Rep Devices covers trunk stock and loaner sets as one process.
Related reading: Trunk stock: from spreadsheet chaos to real-time visibility, Consignment inventory: the hidden P&L risk and the best consignment inventory software in 2026. For the full MedTech picture, see medical device inventory software.
Frequently asked questions
What is trunk stock in medical devices?
Trunk stock is inventory assigned to a sales rep and carried in a vehicle or home office so it is available for cases without a hospital order. It is owned by the manufacturer or distributor until consumed, and billed to the facility after the case, usually through a bill-only purchase order.
What is bill-only in medical device sales?
Bill-only is a purchase order raised by a hospital or ASC after a procedure for an implant the rep supplied from trunk stock or a loaner set. The facility did not stock the item; it pays for what was used. Because the record of use often starts on paper, bill-only is where unbilled and late-billed revenue accumulates.
How often should trunk stock be counted?
Continuously, through scans at assignment and consumption, plus a weekly cycle count of one bin or category prompted by the app. A full physical count once a year confirms the system. Quarterly audit days without scanning produce a snapshot that is wrong by the following Monday.
Why does the 2026 ASC rule matter for trunk stock?
CMS added 289 procedures to the ASC Covered Procedures List for 2026, plus 271 codes removed from the inpatient-only list, and began a three-year phase-out of that list. More orthopedic and spine cases will run in ASCs that do not hold consignment, so reps serve more sites from the same trunk, with more bill-only paperwork and more room for error.
What does trunk stock software need to do?
Record lot, serial and expiry per unit per rep, scan consumption at the point of care, hold par levels and raise replenishment automatically, alert on expiry, work offline, and sync two-way with the ERP (SAP, Microsoft Dynamics, Oracle, NetSuite) so finance keeps one system of record. Ventory does this as the field inventory layer and goes live in 4-8 weeks.
Getting started
Counting every rep's car on a spreadsheet while cases move to ASCs? See how a field inventory layer gives finance and commercial ops the same count, every rep, every lot. Book a demo.
Sources
- CMS, Calendar Year 2026 Hospital Outpatient Prospective Payment System (OPPS) and Ambulatory Surgical Center Final Rule (CMS-1834-FC), fact sheet, 21 November 2025: cms.gov
- Becker's Spine Review, Orthopedic, spine procedures now outpatient-eligible: beckersspine.com
- Ventory Research, MedTech Inventory Visibility Gap Report 2025: ventory.io (PDF)
Ten questions. You get a field readiness score, a gap tier and the three fixes worth doing first.
Ventory is the field inventory layer between your ERP or WMS and the teams working outside the warehouse: engineer vans, forward stocking locations, consigned stock and loaner kits.
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