---
id: KB-NO-025
url: https://app.codecontract.io/help/regulation/changing-a-component-in-a-certified-product
idioma: en
categoria: normativa
subcategoria: producto
audiencia: usuario
nivel: intermedio
actualizado: 2026-08-13
tambienEn: [es]
relacionados: [KB-NO-024, KB-IU-009, KB-NO-018]
citadoPor: [KB-NO-015]
---

# Changing a component in a certified product

_A supplier discontinues a part, you buy the equivalent and carry on selling. The paperwork still describes the old one._

**Responde a:** changed a component do i need to recertify · equivalent part certified product · supplier discontinued a component · when to redo the declaration of conformity

It happens in every company that makes something: a part stops being supplied, you buy the equivalent from the next catalogue and the line keeps running. Nobody did anything odd — it is the sensible call to avoid stopping. The problem shows up months later, when someone compares what is inside the product with what its papers say.

## The four kinds of change, from quiet to loud

| Change | What it usually means |
| --- | --- |
| Same maker, same part number, different batch | Nothing: this is the normal case |
| Same maker, successor part number | Check their data still covers your claims |
| Different maker, «equivalent» part | This is where the real work starts |
| A part touching safety, food contact or the electrical circuit | Stop and check before fitting a single unit |

> [!IMPORTANT]
> «Equivalent» is a purchasing word, not a quality one. **Two parts can be mechanically interchangeable and documentarily not**: same size, same function, and behind them a different certificate, a different material or a test run to another standard. The right question is never «does it fit?» but **«is what I declare about my product still true with this part inside?»**. The first is answered by the warehouse; the second by the technical file.

## What to do on the day of the change, not the day of the problem

1. **Ask the new supplier for the same documentation you held for the old one** — If they cannot provide it, that is already your answer.
2. **Compare it against what your product declares** — Standard applied, material, limit values. Point by point, not from memory.
3. **Record from which serial or batch the new part is fitted** — Without that boundary you cannot contain anything if a review is ever needed.
4. **And update the technical file before the first unit ships** — After that it becomes archaeology.

> [!WARNING]
> The scenario to avoid at all costs is the silent one: **the supplier makes the change and does not tell you**. Same part number, same delivery note, and inside a different material or a different factory. That is why the commitment to notify changes is requested IN WRITING when the supplier is onboarded and not once suspicions arise — and why it pays to keep each component's datasheet with its date: it is the only thing that lets you show what you were being supplied at any given time.

## When the change does force new paperwork

**En corto**

- If it affects what you declare, the declaration is redone: that is not a matter of opinion.
- If the product had test reports, work out which need repeating — almost never all of them.
- And if the product is already on the market, the decision stops being purely technical: who tells whom enters the room.

> [!NOTE]
> Which changes force repeat testing, a new declaration or notifying a body depends on the product and its regulatory framework. **Your adviser or notified body settles that before the part is fitted**; here we explain how not to arrive at that conversation with two hundred units already sold.

**Can I fit an equivalent part while I check?**

It depends what it touches. If safety is anywhere near, the prudent answer is no.

**Does the whole product need recertifying?**

Rarely. The norm is reviewing the affected part, and for that you need the file.

**What if the supplier changed it without telling me?**

Document from when, assess the impact, and revisit the notification agreement with them.

## Ejemplos

**Purchasing swaps in an equivalent part from another maker to keep the line running.**

- Asks the new supplier for the same datasheet and certificate held for the old one
- Compares point by point against what the product declares

→ The change is decided on data rather than on «it fits the same».

**Units already sold need reviewing and nobody knows since when the new part has been fitted.**

- Records the serial or batch number from which each change applies

→ The review is contained to the affected units instead of a whole year's output.

**A supplier changes factory without notice and you find out from a colour difference.**

- Keeps each component's datasheet with its date and requires written change notification

→ You can show what was being supplied when, and claim against something written down.

**A part is substituted and nobody touches the documentation.**

- Reviews which documents describe that part

→ The papers keep describing what is made.

**Nobody knows from which unit the component changed.**

- Records from which batch the new part enters

→ You can say what each unit carried.

**The new part's supplier provides no documentation.**

- Requests it before starting to use it

→ The change does not leave a gap in the file.