NABL assessment preparation comes down to four jobs. Run your laboratory to ISO/IEC 17025:2017. Complete at least one internal audit and a management review before you apply. Read NABL’s process document (NABL 100B) and the specific criteria for your field. And keep records that let an assessor trace any reported result back to the person, method, equipment and calibration behind it. Software can help with the records. It does not make a lab accredited.
NABL accredits laboratories. It does not accredit software, so be wary of any vendor that says NABL has approved its software. Here you will find the NABL documents to read, the records worth keeping and a trace-back test to run on yourself. WebUncles offers calibration management software for the record-keeping part, priced after a demo.
NABL documents to read first
The table lists documents for calibration laboratories as shown on NABL’s documents page when we checked on 14 November 2026. Titles are shortened. Versions change, so always download the current one.
| Document | What it is for | Version listed (checked 14 Nov 2026) |
|---|---|---|
| NABL 100B | Accreditation Process & Procedure | Issue 01 (23/11/2022), amendment 03 (27/08/2025) |
| NABL 129 | Specific criteria for calibration labs (mechanical, fluid flow, radiological, electro-technical, thermal) | Issue 01 (02/04/2019), amendment 01 (01/11/2021) |
| NABL 152 | Application form for calibration laboratories | Issue 14 (25/06/2018), amendment 06 (18/08/2026) |
| NABL 160A | Guide for preparing the management system document or quality manual | Issue 01 (02/01/2026) |
| NABL 161 | Guide for internal audit and management review | Issue 06 (05/02/2020), amendment 02 (21/01/2026) |
| NABL 142 | Policy on metrological traceability of measurement results | Issue 07 (11/01/2021) |
| NABL 143 | Policy on calibration and measurement capability (CMC) and measurement uncertainty | Issue 04 (26/03/2021) |
| NABL 141 | Guidelines for estimation and expression of uncertainty in measurement | Issue 04 (10/02/2020) |
| NABL 164 | Guidelines for interlaboratory comparison where formal proficiency testing is not available | Issue 04 (06/02/2020), amendment 01 (25/10/2021) |
| NABL 219 | Assessment forms and checklist, based on ISO/IEC 17025:2017 | Issue 02 (16/02/2021), amendment 02 (01/09/2025) |
| NABL 220 | Document review checklist, based on ISO/IEC 17025:2017 | Issue 02 (20/07/2020), amendment 02 (22/09/2026) |
Other documents apply to some labs: NABL 126 for medical devices, NABL 138 for air quality monitoring equipment and NABL 130 for site calibration. NABL’s calibration laboratory page lists them with the fee table. NABL 163 sets its policy for proficiency testing participation.
How the NABL assessment process works, in what NABL states
We only describe what NABL’s own pages state. For stages and timelines, read NABL 100B.
- You apply with the form for your field (NABL 152 for calibration), a system document such as a quality manual, and the fee set in NABL 100A, according to NABL’s FAQ page (checked 14 November 2026).
- The FAQ also says the quality manual must satisfy ISO/IEC 17025 and NABL criteria, and that procedures must actually be in use.
- Before applying, a lab should have completed at least one internal audit and a management review (same FAQ page).
- The proposed Quality Manager’s competence is judged during the assessment (same FAQ page).
- NABL has a document review checklist (NABL 220) and assessors use the NABL 219 forms and checklist, both based on ISO/IEC 17025:2017.
- Pre-assessment is now optional, and during the first accreditation cycle the annual on-site surveillance is a desktop surveillance, as stated on NABL’s updates page (checked 14 November 2026).
A useful free step: read NABL 219 and NABL 220 yourself. They show the questions the assessor works through.
The records an assessor can ask to see
ISO/IEC 17025:2017 expects records in many areas. The clause numbers below match the standard’s structure, which NIST also sets out in its 17025 highlights for laboratory directors. The wording is our paraphrase, so check details in your own copy.
| Record | Where it sits in ISO/IEC 17025 | What an assessor may check |
|---|---|---|
| Staff competence and authorisation | Clause 6.2 | Qualifications, training, who is authorised for which calibration, how competence is monitored. |
| Equipment records | Clause 6.4.13 | Identity, manufacturer and serial number, location, calibration dates and results, next due date, maintenance, repairs. |
| Calibration programme and status | Clauses 6.4.7 to 6.4.9 | Due dates met, status visible, doubtful equipment taken out of service. |
| Traceability | Clause 6.5, NABL 142 | Calibration of your reference standards from an acceptable source, with an unbroken chain. |
| Method verification | Clause 7.2 | Evidence that you can perform each method correctly. |
| Technical records of each calibration | Clause 7.5 | Who did the work, when, with which equipment, under which conditions, with raw data. |
| Measurement uncertainty | Clause 7.6, NABL 141 and 143 | Uncertainty evaluation per scope item, consistent with your claimed CMC. |
| Validity of results | Clause 7.7, NABL 163 and 164 | Proficiency testing or interlaboratory comparison results, and follow-up on poor results. |
| Calibration certificates | Clause 7.8 | Copies of what was issued, with the required content, and any amendments. |
| Complaints, nonconforming work, corrective action | Clauses 7.9, 7.10 and 8.7 | What went wrong, the effect, the action taken. |
| Internal audits and management review | Clauses 8.8 and 8.9, NABL 161 | Plans, findings, closure, decisions. |
| Document and record control | Clauses 8.3 and 8.4 | Current versions, retention, protection. |
| Data and IT systems | Clause 7.11 | Validation of systems that record and store data, protection from loss and tampering. |
The trace-back test
The quickest way to find gaps is to work backwards from what you have already issued. Take one certificate and follow it back to the person who did the work, the instrument, that instrument’s own calibration, the method and any later changes. Do it on three certificates before the assessor does:
- Pick a certificate issued last month.
- Find the raw data and the person who recorded it, and check they were authorised for that task.
- Find the instrument record and the calibration certificate that was valid on the day.
- Check the traceability chain of the reference standard used.
- Check the uncertainty is consistent with your scope and CMC.
- Check the certificate content against clause 7.8 (use a clause 7.8 checklist).
- If anything is missing, write down where it should have been kept.
Which records software helps you keep
Software helps most with records that are repetitive, dated and searched by many people. It helps less with judgement.
| Software can help with | Still needs people |
|---|---|
| Equipment list, due dates and status | Deciding calibration intervals and checking results |
| Storing certificates against each instrument | Judging that a certificate is acceptable and traceable |
| Change history with names and times | Deciding whether a change was right |
| Reminders for PT rounds, audits and reviews | Running the audit and making management decisions |
| Search across jobs, instruments and staff | Technical review of results |
| Backup and controlled access | Validating the system for your use (clause 7.11.2) |
If you want to see the left-hand column in practice, book a free demo and bring your equipment list. We will show which of those records our software keeps today.
For a wider look at what ISO/IEC 17025 software should do, read our guide to ISO 17025 calibration software.
A NABL assessment preparation checklist
- Gap check. Compare your system with ISO/IEC 17025:2017 and the NABL criteria for your field.
- Clean the equipment list. Unique IDs, current certificates, due dates, status labels.
- Fix traceability. Confirm each reference standard is calibrated by a source that NABL 142 accepts.
- Complete uncertainty and CMC work for each item in your intended scope.
- Join proficiency testing or interlaboratory comparison where available, and keep the results.
- Write or update the quality manual with NABL 160A as a guide.
- Run an internal audit and a management review using NABL 161.
- Do a mock assessment with the NABL 219 and 220 checklists.
- Apply with NABL 152 and the fee.
Common gaps to look for
- Certificates that show the calibration date but no issue date. A2LA lists the date of issue among common certificate findings.
- Traceability statements that name an institute, such as “NIST traceable”. A2LA’s guidance is to state traceability to the SI instead.
- Uncertainty shown with more than two significant digits, or smaller than the CMC on your scope. A2LA also warns against copying the CMC as the reported uncertainty without justification.
- Records written long after the work, or edited without the original value visible.
- A spreadsheet used for results with no test record.
The A2LA points are from another accreditation body. NABL has its own documents. Use them as ideas to check, not as NABL rules.
What to ask in a demo
- Can I print or export all records for one instrument or one certificate for an assessor?
- Does it keep a change log I cannot switch off?
- Can I set retention and back up the data?
- Can it hold the certificates I receive from calibration providers?
- Can it create the certificates my lab issues, or only store them? (Ask for a live example.)
- Who can view or edit which records?
- How was the system validated, and what do I need to do for clause 7.11.2?
WebUncles’ calibration management software is priced after a demo. We do not publish a figure because the cost depends on your size and needs. If your lab needs a workflow that a standard product does not cover, such as a special record format, we can build it under custom software development.
Frequently asked questions
Does NABL approve calibration software?
No. NABL accredits laboratories, not software products. Software can help you keep the records an assessor asks for, but the accreditation belongs to the lab.
What should I do before applying to NABL?
NABL’s FAQ says a lab should complete at least one internal audit and a management review before applying. You also need the application form for your field, a quality manual and the fee. Read NABL 100B for the process.
Which NABL documents apply to a calibration lab?
Common ones are NABL 100B, NABL 129 (or 126, 138 or 130 for specific areas), NABL 152, NABL 142, NABL 143 and NABL 219. Check the NABL documents page for current versions.
Do I need proficiency testing?
NABL has a policy on proficiency testing participation (NABL 163) and a guideline for interlaboratory comparison where formal programmes are not available (NABL 164). Read both for your field.
Can Excel be used for records?
It can, but systems that record and store data must be validated for use under ISO/IEC 17025 clause 7.11.2. Keep a test record and control changes.
How long does NABL accreditation take?
We do not state a timeline. NABL 100B is the reference for process and stages. Ask NABL for current timelines.
Book a free demo
Run the trace-back test on one certificate first and note where you got stuck. Bring those notes. We will go through them in our calibration management software and say which gaps it can help with today. Book a free demo.
