---
title: Lot Numbering and Traceability Requirements Under MDR
description: Lot numbering is the production identifier that makes MDR Article 25 traceability and recalls actually work. Here is the startup playbook.
authors: Tibor Zechmeister, Felix Lenhard
category: Technical Documentation & Labeling
primary_keyword: lot numbering traceability MDR
canonical_url: https://zechmeister-solutions.com/en/blog/lot-numbering-traceability-mdr
source: zechmeister-solutions.com
license: All rights reserved. Content may be cited with attribution and a link to the canonical URL.
---

# Lot Numbering and Traceability Requirements Under MDR

*By Tibor Zechmeister (EU MDR Expert, Notified Body Lead Auditor) and Felix Lenhard.*

> **Under MDR, the lot number is the production identifier that turns a model-level device identifier into a uniquely traceable physical unit or batch. Annex I Chapter III Section 23 of Regulation (EU) 2017/745 requires the label to carry an indication that allows the device to be identified, including, where appropriate, the batch code or lot number. MDR Article 27 then requires that identifier to be carried by the UDI-PI (Production Identifier) part of the Unique Device Identifier. Together with MDR Article 25 on supply chain traceability, this means every lot number printed on a label must link back, through the QMS and ERP records, to the components, operators, and customers associated with that batch. Lot numbering is not a labeling detail. It is the atom of traceability.**

**By Tibor Zechmeister and Felix Lenhard. Last updated 10 April 2026.**

---

## TL;DR

- Annex I Chapter III Section 23 of Regulation (EU) 2017/745 requires the device label to carry the batch code or lot number (or, where appropriate, the serial number) as part of the identification information that must appear on every device.
- Under MDR Article 27, the lot number is one of the forms the UDI-PI (Production Identifier) can take, sitting alongside the UDI-DI (Device Identifier) to make each production unit uniquely identifiable across the EU.
- MDR Article 25 is the legal obligation that makes the lot number matter in practice: every economic operator must be able to trace one step up and one step down in the supply chain for the retention periods in Article 10(8).
- Lot tracking is the right choice when every unit in a production batch is interchangeable for traceability purposes — typical for sterile single-use consumables, many Class I and Class IIa devices, and most active non-implantable equipment produced in runs.
- A lot numbering system only works if the number on the label, the number in the ERP, the number in the shipping record, and the number in the complaint file are the same string — and if the link between the lot and its components, operators, and customers is queryable in minutes, not days.

---

## Why the lot number is the smallest unit of traceability

A Notified Body auditor sits down at the QMS laptop, opens the label archive, and reads off a lot number from a device that shipped six months ago. "Tell me which customers received this lot. Tell me which component lots went into it. Tell me which operators worked on it. Show me the release record." The answer determines whether the audit ends with a certificate or a major non-conformity.

This is not a theoretical scenario. It is the single most diagnostic test of a medical device QMS, and the lot number is the query key. When the lot number on the label does not match the lot number in the ERP, the system is broken no matter how elegant the rest of the QMS looks. When the lot number matches but the link from lot to components is missing, a single supplier defect can freeze an entire inventory with no way to narrow the scope. When the lot to customer link is maintained as a shipping spreadsheet on someone's laptop, the first recall will expose it.

Lot numbering is the cheapest part of an MDR-compliant QMS to get right at the start and one of the most expensive to fix later. Every record carrying the wrong format, every ERP table keyed on the wrong field, every label template that separates the lot from the UDI is technical debt that compounds. The post below is the playbook for getting it right on the first production run.

## Lot, serial, and UDI-PI — what the MDR actually distinguishes

MDR does not use the words "lot" and "serial" as loose synonyms. They are specific identifier types with specific applications, and the choice between them is made at design time.

A **lot number** (also called batch code or batch number) identifies a group of units produced under conditions considered sufficiently uniform that, for traceability purposes, they can be treated as a single batch. Every unit in the lot shares the lot number. Lot tracking is appropriate when failure analysis and corrective action would naturally address the whole batch — sterile single-use consumables, packaged reagents, most Class I devices, many Class IIa devices produced in runs.

A **serial number** identifies a single individual unit. No other unit shares it. Serial tracking is appropriate when failure analysis and corrective action need to address individual units — reusable instruments, active devices, capital equipment, implantable devices, anything where the life cycle of one unit diverges meaningfully from its neighbors.

The **UDI-PI** — the Production Identifier under MDR Article 27 — is the umbrella for both. MDR Article 27 defines the UDI as comprising two components: the UDI-DI, which is unique to the manufacturer and the device model (including the packaging level), and the UDI-PI, which identifies the unit of device production and, where applicable, the packaged devices. The UDI-PI can take the form of the lot number, the serial number, the software identification, the manufacturing date, the expiry date, or a combination of these.

In practice, for a lot-tracked device, the UDI-PI is the lot number combined with the manufacturing date or expiry date as required by the issuing entity's encoding rules. For a serial-tracked device, the UDI-PI is the serial number. Some devices carry both: a lot for the sterilisation batch plus a serial for the individual instrument. The choice is driven by the device type, the risk class, the failure modes, and the obligations under MDR Article 25.

For the orientation on how the UDI-DI and UDI-PI fit together, read [UDI-DI vs UDI-PI: what the two identifiers mean](/blog/udi-di-vs-udi-pi).

## MDR Article 25 — where lot numbers meet supply chain traceability

Article 25 of Regulation (EU) 2017/745, "Identification within the supply chain," is the legal obligation that makes the lot number matter once the device leaves the factory. Economic operators must be able, for the retention period referenced in Article 10(8), to identify any economic operator to whom they have directly supplied a device and any economic operator who has directly supplied them with a device, as well as any health institution or healthcare professional to which they have directly supplied a device.

The retention period in Article 10(8) is a minimum of ten years after the last device covered by the EU declaration of conformity has been placed on the market, extended to fifteen years for implantable devices.

Article 25 does not say "lot number" explicitly — it talks about identifying devices and operators. But the practical enforcement is always through the identifier printed on the label and recorded in the shipping system. A competent authority asking "who received lot 24B117?" is asking an Article 25 question, and the answer has to come out of the manufacturer's records in a usable form. This is why the lot numbering scheme must be tightly coupled to the distribution records: every shipment out of the facility records the UDI-DI, the UDI-PI (lot or serial), the recipient, and the date, in a single queryable system.

For the full reading of Article 25 and the traceability chain, see [MDR Traceability Requirements and the ISO 13485 clauses](/blog/mdr-traceability-requirements).

## Annex I Chapter III Section 23 — the label obligation

Annex I Chapter III Section 23 of Regulation (EU) 2017/745 is the part of the General Safety and Performance Requirements that governs the information supplied with the device. Section 23.2 sets out the mandatory information to appear on the label, and among the identification elements, it requires an indication that enables the user to identify the device — including the name or trade name of the device, the details required to allow the user to identify the device, the contents of the packaging, any specific conditions of use, and the batch code preceded by the word "LOT", or the serial number, as appropriate.

The phrasing matters. For lot-tracked devices, the word "LOT" (or its symbolic equivalent from the harmonised symbol standard) must appear next to the identifier on the label. For serial-tracked devices, "SN" (or the symbolic equivalent) appears. The identifier itself must be human-readable and, under MDR Article 27, also carried in the UDI-PI portion of the UDI carrier (typically a GS1 DataMatrix or linear barcode).

The mistake to avoid: printing the UDI barcode correctly but forgetting to print the human-readable lot number next to the "LOT" symbol, or vice versa. The label must carry both. The harmonised symbol standard used for the LOT and SN icons is widely implemented via EN ISO 15223-1, but the underlying obligation is MDR Annex I Section 23 itself — the standard is the tool, the regulation is the requirement.

## ERP integration — where lot numbering either works or collapses

A lot numbering scheme that lives only on the label is not a traceability system. It is a sticker. The system becomes real only when the same lot number is the primary key in the ERP, the MES, the QMS, and the shipping records — all pointing back to the same physical batch.

A startup's lot numbering scheme should satisfy five conditions.

**Uniqueness across the company lifetime.** No two production batches ever share a lot number, including across different devices, different years, and different sites. The cheapest way to achieve this is a scheme that encodes the year and the sequential batch number (e.g., `24B117` = year 2024, product line B, batch 117). Recycling lot numbers after a fixed period is a recipe for ambiguity in archived records — and Article 10(8) retention periods are long enough that the ambiguity will eventually bite.

**Machine readability.** The lot number format must be compatible with the UDI-PI encoding rules of the issuing entity. GS1 Application Identifier (10) for batch/lot carries up to 20 alphanumeric characters. Staying inside the common encoding constraints means the same string works on the label, in the barcode, and in every downstream system.

**ERP as the system of record.** Every production order in the ERP creates a lot record at the moment the batch is opened. The lot record is the parent row; component consumption, operator steps, in-process tests, release decisions, shipment lines, and complaint links all reference the same lot ID. When the lot is released, the label print job reads the lot number from the ERP — it is not retyped by a human.

**Backward linkage to components.** Every component consumed into a lot is recorded against the lot, with the supplier's lot number (or serial, or batch) captured at goods receipt and carried through production. When a supplier reports a defect in a specific component batch, a single query returns the list of finished lots affected.

**Forward linkage to customers.** Every shipment line records the lot number, the UDI-DI, the recipient, and the date. When a recall is required, a single query returns the list of customers who received the affected lot.

These five conditions are not an ERP vendor pitch. They are the operational restatement of MDR Article 25 and the ISO 13485 clauses 7.5.8 and 7.5.9 from the perspective of the person who has to run the query at three in the morning during a field safety corrective action.

## Test — a recall scenario that shows why lots matter

A startup making a Class IIa single-use sterile consumable ships thirty thousand units over eighteen months across seven EU countries. On a Tuesday morning, the sterilisation service provider reports that one of their cycles was compromised: the biological indicator failed a post-release retest, and all product sterilised in that cycle is at risk of non-sterility. The cycle processed three production batches from this manufacturer.

The question the competent authority asks, and that the manufacturer must answer inside a few hours, is: which customers received units from those three batches, and how many units in total?

If the lot numbering is tight, the answer is a single ERP query. The three batch numbers are known from the sterilisation service provider's records. The shipment lines referencing those batches return a list of customers, quantities, and dates. The manufacturer issues the field safety notice, sends the recall letters, and opens the vigilance case with full scope clarity inside the afternoon.

If the lot numbering is loose — if shipments were recorded only by the device reference and not by the batch, or if the sterilisation batches were not linked to the production lots, or if the customer master record is a tab in a spreadsheet — the manufacturer spends three days reconstructing the scope from email threads and shipping receipts. The recall notice goes out with hedged language ("all units shipped between January and March"), covering ten times more inventory than necessary. The customers lose confidence. The competent authority opens a broader investigation into the QMS. The Notified Body is notified and schedules an unannounced audit.

The difference between the two outcomes is five integer columns in an ERP schema, set up correctly on day one.

## Ship — the lot numbering playbook

The playbook for a startup setting up its lot numbering scheme before the first production run.

1. **Decide lot vs serial per device, in writing, at design time.** Document the choice in the traceability procedure that implements EN ISO 13485:2016+A11:2021 clauses 7.5.8 and 7.5.9. Link the decision to the risk classification, the failure modes, and the Article 25 obligation.
2. **Design the lot number format before the first label template.** Year + product code + sequential batch number is a safe default. Avoid formats that embed meaning you may later want to change (e.g., site codes for a single-site startup — fine; line codes for a startup with one production line — unnecessary).
3. **Make the ERP the system of record.** Every production order creates a lot. Every label print reads the lot from the ERP. No handwritten lot numbers, ever.
4. **Capture supplier lot numbers at goods receipt.** The link from finished lot to component lot is the difference between a targeted recall and a total inventory freeze.
5. **Capture the lot number on every shipment line.** The UDI-DI is not enough. The UDI-PI is the field that makes Article 25 queries work.
6. **Print the label with the LOT symbol and the human-readable lot number next to the UDI barcode.** Verify that the barcode encodes the same lot number that appears in human-readable form. This is the single most common labeling finding in early-stage Notified Body audits.
7. **Archive the lot records for the full Article 10(8) retention period.** Ten years minimum from the last unit placed on the market. Fifteen years for implantable devices. Test the archive by retrieving a record at least annually.
8. **Simulate a recall once a quarter.** Pick a random lot number from six months ago, run the full upstream-and-downstream trace, time it, and log the result in the PMS system. The first time you do this, you will find at least one broken link. That is the point of the exercise.

## Reality Check — Where do you stand?

1. Pick a lot number from a device you shipped six months ago. Can you produce, within one hour, the full list of component lots consumed into that production batch and the full list of customers who received units from it?
2. Is the lot number on your label, on your barcode, in your ERP, on your shipping record, and in your complaint files the same exact string in every system?
3. Does your ERP create the lot at the moment the production order opens, or is the lot number assigned separately and retyped into the system later?
4. Does every shipment line in your distribution records carry the UDI-PI (lot number), or only the UDI-DI and the quantity?
5. For your most recent goods receipt of a critical component, is the supplier's lot number captured and linked to the specific finished lots that consumed that component?
6. Does your label carry the LOT symbol (or SN for serialised devices) next to a human-readable identifier, as required by Annex I Chapter III Section 23 of Regulation (EU) 2017/745?
7. Have you ever simulated a recall scoped by lot number and timed the query, or is the first time you will do this during an actual field safety corrective action?

## Frequently Asked Questions

**Is the lot number mandatory on every medical device label under MDR?**
The label must carry a batch code or lot number, or a serial number, as appropriate for the device. Annex I Chapter III Section 23 of Regulation (EU) 2017/745 specifies this as part of the mandatory identification information on the label. Which identifier applies depends on whether the device is lot-tracked or serial-tracked.

**What is the difference between a lot number and the UDI-PI?**
The lot number is one of the forms the UDI-PI (Production Identifier) can take under MDR Article 27. The UDI-PI is the regulatory concept; the lot number is the specific type of identifier used for batch-tracked devices. For serial-tracked devices, the UDI-PI is the serial number.

**How long must I keep lot records?**
At least ten years after the last unit covered by the declaration of conformity has been placed on the market, and fifteen years for implantable devices, under MDR Article 10(8). Article 25 traceability records are held by every economic operator in the chain for the same periods.

**Can I reuse lot numbers after a few years?**
No. Retention periods under Article 10(8) are long enough that reused lot numbers will create ambiguity in archived records. The lot number format should guarantee uniqueness across the full company lifetime, typically by encoding the year in the identifier.

**Does the lot number have to match the UDI barcode exactly?**
Yes. The human-readable lot number printed next to the LOT symbol and the lot number encoded in the UDI-PI portion of the barcode must be the same string. A mismatch between the two is one of the most common labeling non-conformities in Notified Body audits.

**What if my device is both lot-tracked and serial-tracked?**
Some devices carry both — for example, a sterile packaging run identified by lot plus an individual instrument identified by serial inside. In that case, the label carries both identifiers and both are captured in the ERP and the shipping records. The traceability procedure documents the relationship.

## Related reading

- [MDR Traceability Requirements: How ISO 13485 Supports Device Tracking](/blog/mdr-traceability-requirements) — the full reading of Article 25 and the ISO 13485 clauses 7.5.8 and 7.5.9 that sit behind every lot numbering decision.
- [UDI-DI vs UDI-PI: What the Two Identifiers Mean](/blog/udi-di-vs-udi-pi) — the orientation to how the device identifier and production identifier fit together, with the lot number as one form of the UDI-PI.
- [Recalls Under MDR: Withdrawing a Device From the Market](/blog/recalls-mdr-withdrawing-device-from-market) — how a well-designed lot numbering scheme turns a recall from a crisis into a query.

## Sources

1. Regulation (EU) 2017/745 of the European Parliament and of the Council of 5 April 2017 on medical devices, Article 10(8) (retention periods), Article 25 (identification within the supply chain), Article 27 (Unique Device Identification system), Annex I Chapter III Section 23 (information supplied by the manufacturer on the label and in the instructions for use). Official Journal L 117, 5.5.2017.
2. EN ISO 13485:2016+A11:2021 — Medical devices — Quality management systems — Requirements for regulatory purposes. Clause 7.5.8 (Identification) and clause 7.5.9 (Traceability).

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*This post is part of the Technical Documentation & Labeling category in the Subtract to Ship: MDR blog. Authored by Tibor Zechmeister and Felix Lenhard. The MDR is the North Star. A lot number is the smallest unit of traceability — get the scheme right on day one, and every downstream obligation becomes a query instead of a crisis.*

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*This post is part of the [Technical Documentation & Labeling](https://zechmeister-solutions.com/en/blog/category/technical-documentation) cluster in the [Subtract to Ship: MDR Blog](https://zechmeister-solutions.com/en/blog). For EU MDR certification consulting, see [zechmeister-solutions.com](https://zechmeister-solutions.com).*