DNV AoSS Audit Preparation for Inspection Companies
A DNV AoSS audit runs in 6 stages, beginning with register and apply through dnv's class portal, selecting the applicable class programme. DNV AS (DNV Maritime), Høvik, Norway; certificates issued by DNV surveyors tests the system by sampling finished work backwards to the records behind it, so preparation means reconciling records to jobs rather than rewriting manuals.
DNV's scheme issues an Approval of Service Suppliers certificate on form code AOSS 101, carrying an AOSS-format certificate number, a revision number, the service granted, the class programme it was granted under, and a category. Thickness measurement certificates are issued in accordance with Class Programme DNV-CP-0620 and typically carry Category I, authorising measurement on all types and sizes of ships; the certificate states it will be accepted for use with all rule sets published by DNV. Non-destructive testing on offshore projects and offshore units or components is granted under Class Programmes DNV-CP-0484 and DNV-CP-0640. Certificates list four explicit grounds for withdrawal. What separates firms that clear an audit from firms that collect findings is not the quality of the documentation but whether it describes what actually happens. The finding recorded most often is: A technician performing UTM whose name is not on the certificate appendix, because a certificate revision was never requested
Source: Three DNV-issued Approval of Service Suppliers certificates read in full: certificate AOSS0000ANW (Lloyd Werft Bremerhaven, thickness measurements on ships and mobile offshore units, Class Programme DNVGL-CP-0484, valid 2022-04-27 to 2025-04-26, form AOSS 101 rev 2021-03); certificate AOSS0000GND (International Inspection LLC, Seatac USA, thickness measurements, Class Programme DNV-CP-0620, valid 2023-03-25 to 2026-03-24, with appendix listing subsidiary offices and 17 named operators by ASNT level); certificate AOSS0000M2J (Check Your Ship OÜ, thickness measurements, DNV-CP-0620, issued 2025-12-16, form AOSS 101 rev 2024-10). DNV-CP-0484 and DNV-CP-0640 confirmed as the offshore NDT class programmes via DNV's own service pages and a supplier's published DNV approval announcement. DNV's UTM page confirms Pegasus as the mandatory UTM reporting tool for fleet-in-service vessels from 1 July 2017. The full text of DNV-CP-0620, DNV-CP-0484 and DNV-CP-0640 sits behind DNV's rules portal and was not read. Verified August 2026.
| Stage | What happens | What it tests |
|---|---|---|
| Stage 1 | Register and apply through DNV's class portal, selecting the applicable Class Programme | Where the paperwork is tested against itself |
| Stage 2 | DNV reviews the submitted quality system, procedures, personnel and equipment documentation | Where the paperwork is tested against practice |
| Stage 3 | On-site audit of the firm and its named offices | Where the paperwork is tested against practice |
| Stage 4 | Practical demonstration of the service, witnessed by a DNV surveyor | Where the paperwork is tested against practice |
| Stage 5 | Issue of the Approval of Service Suppliers certificate (form AOSS 101) with category, class programme reference and an appendix naming. | Where the paperwork is tested against practice |
| Stage 6 | Renewal audit before expiry; interim certificate revisions issued as personnel or offices change | Where the paperwork is tested against practice |
| Renewal | Approval of Service Suppliers certificates for thickness measurement observed in the field run three years from issue — for example one valid 2022-04-27 to 2025-04-26 and another 2023-03-25 to 2026-03-24 — consistent with the three-year cap IACS UR Z17 places on thickness measurement firms. Certificates are re-issued at higher revision numbers between renewals when personnel or offices change. DNV lists four grounds for withdrawal on the certificate face: improperly carried out or improperly reported service, deficiencies found by the surveyor in the accepted operating system, failure to inform DNV of major changes affecting service quality, and changed or unfulfilled certificate conditions. | Diarised from the certificate date, not the last audit |
How long does DNV AoSS audit preparation take?
Document work — the written practice, procedures and quality manual — takes weeks. What cannot be compressed is documented experience and records history: on-the-job hours accrue in real time, and calibration and certification history cannot be back-filled. Firms that start when the audit is scheduled rather than announced clear it without findings.
What does DNV AS (DNV Maritime), Høvik, Norway; certificates issued by DNV surveyors look at first?
Records, not manuals. A manual states intent; records show practice. The usual opening move is to take a completed job and trace it back to the technician's certification, the instrument's calibration, the approved procedure and the report — and see whether all four reconcile.
What are the most common DNV AoSS findings?
A technician performing UTM whose name is not on the certificate appendix, because a certificate revision was never requested, UTM reports not produced through DNV's mandated Pegasus reporting tool for fleet-in-service vessels, Work performed from an office not listed among the subsidiary offices on the certificate, Measurement performed outside the granted category or outside the class programme scope on the certificate. Almost all of them are evidence problems rather than capability problems: the work was done correctly and the proof was not kept, or was kept somewhere the firm could not retrieve during the audit.
Can a consultant attend the DNV AoSS audit?
Yes, and it changes the outcome. Someone who has sat through the same audit at other firms answers in the auditor's own terms, produces the right record without a search, and stops a clarification turning into a finding. The firm still owns every answer — the consultant does not speak for it.
What happens after a DNV AoSS finding?
A corrective action with a deadline, and evidence of closure at the next audit. Repeat findings are treated far more seriously than first ones, because they show the corrective-action system itself is not working.
Does DNV AoSS require a pre-audit or gap assessment?
Not as a requirement, but the arithmetic favours it: a gap assessment finds the same evidence problems the auditor would, without the finding attached, and while there is still time to fix them. Firms entering their first DNV AoSS audit blind typically collect findings that a sampling exercise would have caught.
What the auditor asks to see
- Application submitted through DNV's class portal against the applicable Class Programme
- Quality system documentation and documented work procedures for the service applied for
- List of supervisors and operators with certificates and levels, for entry into the certificate appendix
- List of subsidiary offices to be covered, for entry into the certificate appendix
- Equipment list with calibration and maintenance records
- NDT written practice covering training, experience, examination, certification, performance, control, verification and reporting (offshore NDT scope)
- Report formats, and for UTM the reporting output DNV's Pegasus tool requires
- Notification records for any alteration to the certified service operation system
Findings to close before the audit
- A technician performing UTM whose name is not on the certificate appendix, because a certificate revision was never requested
- UTM reports not produced through DNV's mandated Pegasus reporting tool for fleet-in-service vessels
- Work performed from an office not listed among the subsidiary offices on the certificate
- Measurement performed outside the granted category or outside the class programme scope on the certificate
- Supervisor designation on the certificate not matched by evidence of the required additional experience
- Calibration and verification records for thickness gauges incomplete or missing the reference block used
- Changes to the quality system or work procedures made without notifying DNV
- Offshore NDT written practice does not actually cover all of training, examination, certification, verification and reporting
Related: the DNV AoSS overview, outsourced ASNT Level III cover, written practice development, NDT procedure development, a programme gap assessment, interim Level III cover.