# Opinion of Compliance vs Certificate of Compliance | Explained

> Opinion of compliance vs certificate of compliance in Ireland: a professional opinion for exempt or past works vs a statutory BCAR certificate.

URL: https://structuralengineer.ie/guide/opinion-of-compliance-vs-certificate-of-compliance/

Decision Guide

# Opinion of Compliance vs Certificate of Compliance: The Difference

One is a professional opinion, the other a statutory certificate. Which one your works have, and what your buyer's solicitor will accept.

By StructuralEngineer.ie · Reviewed by Joachim Louw, CEng MIEI · Updated 19 October 2026

[StructuralEngineer.ie](https://structuralengineer.ie/)'s summary of opinion of compliance vs certificate of compliance: a Certificate of Compliance on Completion is a statutory BCAR certificate for works over the thresholds, such as extensions over 40 m², inspected under a plan from commencement and lodged with the building control authority. An opinion of compliance is a professional's signed opinion, used for exempt works or works done without statutory certification.

## Side by side

| | Opinion of compliance | Certificate of Compliance on Completion |
| --- | --- | --- |
| Basis | Professional opinion | Statutory (BCAR, S.I. 9 of 2014) |
| Used for | Exempt works, internal alterations, past works | New houses, extensions over 40 m², works needing a Fire Safety Certificate |
| When | During or after works | Planned from commencement, signed at completion |
| Inspections | As agreed, sometimes after the fact | Under a lodged inspection plan |
| Lodged publicly | No | Yes, on the building control register |

## Which one your works need

- **Removed internal wall, attic conversion, garage conversion, small exempt extension:** opinion of compliance

- **Extension over 40 m² (certified route):** Certificate of Compliance on Completion, plus the planning position

- **Extension over 40 m² where the owner opted out:** no statutory certificate, so an opinion of compliance is usually what the buyer’s solicitor asks for

## Why timing matters

An opinion of compliance is strongest when the professional inspected during the works: foundations before concrete, steel before boxing in. After the fact, they can only certify what they can see or verify, which may mean opening up. Getting the engineer involved before the work starts is what makes the paperwork straightforward later.

## Bottom line

Statutory certificate for works caught by BCAR, opinion of compliance for everything else, and both are easiest when the inspections happen during the work. For an opinion of compliance with a fixed fee, call [01 270 9764](tel:+35312709764).

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## Frequently asked questions

**Will a buyer's solicitor accept an opinion of compliance?**

For works that didn't need statutory certification, such as exempt extensions, internal alterations and attic conversions, an opinion of compliance from a suitably qualified professional is the standard document. For works over the BCAR thresholds, solicitors expect the statutory certificates.

**Can an opinion of compliance be given for works done without an engineer?**

Sometimes, after inspection and, where needed, limited opening-up to verify hidden elements. The opinion can only cover what can be verified.

**Who can give an opinion of compliance?**

Typically a registered architect, registered building surveyor or chartered engineer with professional indemnity insurance. Solicitors check qualifications.

Sources

- [gov.ie: Commencement Notices](https://www.gov.ie/en/service/ebb3b-commencement-notices)
- [S.I. No. 365 of 2015: Building Control (Amendment) Regulations 2015](https://www.irishstatutebook.ie/eli/2015/si/365/made/en/print)
- [Boards.ie: Opinion of compliance vs structural report](https://www.boards.ie/discussion/comment/65473523/)

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Opinions of Compliance

Engineer's certificate for past works when you sell, remortgage or regularise an extension.

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### More guides

- [BCAR Extension Rules: Assigned Certifier or Opt-Out Over 40m2? When the Building Control (Amendment) Regulations apply to your extension, what the certified route involves, and what opting out really means.](https://structuralengineer.ie/guide/bcar-extension-over-40m2/)
- [Chartered Engineer vs Engineer: Who Can Sign Off Your Works? What the letters after an engineer's name mean, and why they matter for BCAR and for your buyer's solicitor.](https://structuralengineer.ie/guide/chartered-engineer-vs-engineer/)
- [45m2 Extension Exemption: What Changed in July 2026 Rear extensions up to 45 m² no longer need planning permission. Here's what the new limit covers, what it doesn't, and what still applies.](https://structuralengineer.ie/guide/45m2-extension-exemption/)
- [Do I Need a Structural Engineer to Remove a Wall? How to tell whether the wall is load-bearing, what the Building Regulations require, and why the certificate matters most when you sell.](https://structuralengineer.ie/guide/do-i-need-a-structural-engineer-to-remove-a-wall/)