Calibration Audit Questions and Audit Sequence That We Need to Know

with 13 Comments
Audit Schedule

As a calibration tech or Engineer, our responsibility does not end after we performed instrument calibration. One of our responsibility is also to respond to or support an audit. 

As per my experience, the most audited processes in the manufacturing industry is the calibration program. One of the main reason is that it is one of the requirement of ISO Standards like ISO 9001 under clause 7.1.5 and ISO 17025:2017 under clause 8.8.

Calibration audit is one of the challenging parts (if not interesting) in internal calibration management if you have a huge company. Almost all areas in the manufacturing floor, calibration audit are expected. Like for example during equipment maintenance, or just even an operator interview. 

Do you  felt uncomfortable every time there is a scheduled audit because you are not sure about your preparations for your calibration program?

Do you always prepare for an incoming audit only to find out you have non-conformances?

Auditors are not the same, some send their checklist first in advance and some only forward their schedule without the audit checklist.

But regardless of they send an audit checklist or not, we should know what to expect from the auditors.

In this post, I will share with you the most asked questions during a calibration audit that I repeatedly encountered. I will also share the audit sequence that I observed that can help us identify or expect the next audit move or questions.

By identifying all these things and prioritizing its completion, it will help us maintain and prepare more ourselves and our internal calibration lab to pass every audit. (Not a 100% assurance but it is an advantage to know in advance)

In any case, whenever an audit comes, you are already prepared. You can use below questions as an internal audit checklist to perform a self-audit if you are implementing either ISO 9001:2015 calibration audit requirements or ISO 17025 audit requirements.

The Calibration Audit Questions

In the past company that I worked for as a Calibration Engineer, managing an in-house calibration lab, I always make sure that all documentation that are always checked during audits are regularly updated. 


Because almost every month, we expect an audit, either from internal audit, a 3rd party auditor certifications (ISO 9001 calibration audit) or a customer audit.

As a calibration engineer, our calibration program is in the best shape if we satisfy the queries of our customers, the user of instruments, and the quality personnel, who require us to support them during  calibration related audits.

As much as possible, we do not want any audit findings because sometimes, even this is an opportunity for improvement to us, it looks like we are incompetent.

This is one reason almost half of our time is dedicated to updating and completing documentation.

Below are some actual audit questions that I gathered, I based most of it from a vendor audit checklist usually related to ISO 9001 calibration audit checklist. This is not a complete list of questions but I believe it touches most of the critical points. 

1. Are there documented procedures for control of inspection, measuring, test equipment? Including:

(a) Equipment master list

(b) Calibration schedule

(c) Calibration interval 

(d) Recall list

(e) Calibration record/report

(f) Calibration methods

2. Is the calibration conducted under the specified environmental conditions?

3. Is the personnel in charge of calibration been trained and formally certified?

4. Is equipment verified or re-calibrated at appropriate intervals?

5. Are measuring equipment safeguarded from unauthorized adjustment or re-adjustment?

6. Is there an official approval control system for all equipment to determine accuracy and precision?

7. Are measuring and test equipment re-calibrated when found not meeting the requirement?

8. Are instruments that do not need calibration clearly labeled as such? (Check related post in this link)

9. Are the reference standards or reference materials used for calibrations correctly stored, managed and traceable to International standards (i.e.  NIST)? – Managing a reference standard includes transport, preventive maintenance, and receiving.

10. Is the master standard for internal calibration has the adequate capability (i.e. 10x higher resolution or with a TUR of greater than 4:1)

11. Is there an appropriate method for storing measuring equipment, tools, and jigs?

12. If a product has been used or tested with equipment found to be out of calibration, is there a process for proper disposition?

13. In case there is a “failed” result in the calibrated equipment, does the procedure define the disposition? – Disposition in this case means, what will you do to the instrument once it failed, do you adjust and return to service with limits or destroyed it (or donate it) and change to new one?

14.  Is there a review process before accepting the services of a 3rd party calibration lab?

15. Are the internal calibration procedures used periodically reviewed and updated?

16. Can you show the measurement traceability (the unbroken chain of comparison) of your reference standards?

17. Is the access to the calibration laboratory effectively controlled?

18. Do you perform intermediate check for your reference standards?

The Calibration Audit Sequence


Actual customer audit
Actual customer audit

Customer audits are the most frequent audits that we encounter in the past company I worked, a manufacturer of ICs (Integrated Circuit) for various usage,  so every now and then a customer audit is expected.

One observation during the audit is that there is a specific audit sequence. These sequences happen most of the audit that I encountered and it is a very helpful guide to trace down the things that are expected to be asked, and in return, we can prepare for it.

Here are the sequences:

First, they will asked for a master list to check if you have a proper monitoring. The Master list is a record of all the instruments for calibration with all the important details like serial #, location, calibration date/due date, etc.

Secondthe auditor will sample an instrument from that list, the sampled instrument will be inspected for:

  • The calibration label or ID if it is still within the calibration date.
  • The exact details as mentioned in the master list
  • Any calibration seals or broken seals

Third, they will ask for its calibration report.

  • The auditor will see to it that there is no out-of-tolerance reported or displayed in the report.
  • They will check the traceability information 
  • Match the details about the sample like the identification tag or serial number reflected in the label.
  • Other important details including who performs the review once received from the 3rd party lab (this is where we must  be knowledgeable on how to understand and interpret a calibration certificatecheck it out here)

Lastly, they will check who performed the  calibration of the instruments, 

  • if internal, they will ask for the training records, the procedure used, and the calibration certificate of the reference standard used for calibration (in which should be also calibrated by a 3rd party lab under ISO 17025 to ensure traceability)
  • if it is external or  3rd party calibration, they will ask for the accreditation certificate with the scope of accreditation of the Lab (should be accredited to ISO 17025).

These audit sequences are what I mostly observe, the sequence may not exactly in those orders but the majority follow it because of the continues thought process that it can provide to the auditors.

By determining these sequence, it presented on what to improve in my calibration program by focusing on every related detail on the sequence as applicable to every measuring instruments that are being used.


I have presented here the audit questions that I encountered during my time as a Calibration Engineer for an In-house calibration lab following the calibration requirements of ISO 9001 and TS 16949 Standards.
It may be a different industry but I believe the calibration program is almost the same to all. I also share the sequences that I observe that could help us understand more what to expect and prepare during a calibration audit.

These are the things to be expected to be asked during the audit but it is not a complete guide to ensure a properly managed calibration lab. Calibration laboratory management has a dedicated international standard to be used for in-depth knowledge of its management, the ISO 17025. If you want to be accredited as a calibration lab then this is the standard to be used.

Do you have other observation and question guides in mind? Please comment below.

Thank you for visiting my site, please leave a comment, subscribe and share.

Best Regards,


13 Responses

  1. PS LIM
    | Reply

    Hi Edwin,

    Do you have any idea on including the decision rule as per requirement of iso17025:2017.
    As for now we are practicing whereby the calibration results + uncertainties between the tolerance.
    There is somehow might be some cases where the calibration results + uncertainties were found out of tolerance on the high side or low side. (the calibration measured value is between tolerance) (the uncertainties caused the value to be out of tolerance)
    Do you have any guidance where i could study on how should we apply these decision rule for our lab requirement.

    • Mick
      | Reply

      Hi Edwin and PS LIM,

      Firstly, Edwin, I would like to mention well done on assisting others in questions and queries relating to audits and many more I viewed recently.

      I’m not sure if you have assisted with PS LIM’s query, I’ll assist anyway.

      PS LIM, I am in the same boat and find it complex with so many choices and facts to consider, however for a basic and not too complex method download these for free ILAC-G8:03/2009 as a starter and Guide 98-4 for using uncertainty in conformity assessment. There’s plenty more, these relate to what you’re doing above.
      However, you must inform the end user of the decision rule when applying it.
      Hope this helps.

      • Hi Mick,

        I guess missed this one.:-)

        Thank you for visiting my site and assisting on this matter, I very much appreciate it.

        I hope that you can provide more assisstance and learn with each other.

        Best Regards,

  2. sujatha
    | Reply

    Good article
    so familiar with our audits

    • Hi Sujatha,

      Thanks, appreciate your time reading my post.

      Best Regards,

  3. jamal
    | Reply

    Good subject
    so familiar with our audits


    • Hi Jamal,
      Yes, these questions are actual questions that I compiled. Thanks for reading my post.

      Best Regards,

  4. Siva Kumar
    | Reply

    Dear Edwin,
    Nicely, what are main point should audited that points you given.
    Thank you.

    Best Regards,
    Siva Kumar

    • Hi Siva,
      If you are implementing calibration or managing a calibration lab, either internal or external lab, all the audit questions that I listed are essential and considered the main points. Each of the questions is referring to a specific process inside a calibration lab and therefore treated as main points. If you cannot meet any of the requirements, it will lead to a non-conformance.

      Thanks for reading my posts,


  5. Rose
    | Reply

    Hi Edwin
    Great stuff!
    Can give us some questions on competency, authority matrix, validity of results, method validation, verification, external providers

    • Hi Rose,

      I will note your concern on my list of future posts. I will inform you once available.

      Thanks for reading.

  6. Negmar
    | Reply

    Think you for sharing your experience.

    • Hi Negmar,
      You are welcome.

      Best regards,

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