The two get used interchangeably on site, and on most days it doesn't matter. It matters at tender, when the question is "what's your QA system?", and it matters at month-end, when the superintendent wants the records before certifying the claim. So it's worth being precise.
Quality assurance is the system
QA is the documented system that sets out how quality will be managed and proven: the quality management plan, the ITP for each work activity, the intervention levels (hold points, witness points, surveillance), who inspects, who witnesses, and what records are kept. QA exists before the work starts. On most civil contracts the principal's representative approves the ITPs before the activity begins – the QA system is part of what you've contracted to deliver, not an internal preference.
Quality control is the checking
QC is the inspection and testing itself: the compaction test on the lot, the pre-pour inspection, the dimensional check on the panel, the megger test on the board. QC happens during and after the work, against the acceptance criteria the ITP set. Where QA says a density test is required at this point and NZTA's spec sets the pass mark, QC is the technician taking the test and the result coming back.
The two meet in the record. A completed ITC is QC results captured inside the QA structure: the ITP said what would be verified; the completed checklist proves it was, with results, dates, and signatures against each item.
Why the difference matters commercially
Two reasons, both money.
The tender asks about QA, not QC. Every contractor tests concrete. The scored question is whether you have a system – ITPs aligned to the spec, records the client can audit, a process a new crew can follow. A binder of blank templates answers it badly. A live record from a current job answers it well.
The claim is released on QA records. On QA-gated contracts, the superintendent or engineer's representative certifies each claim line against the conformance records behind it – the completed checklists, the released hold points, the test results. A lot with a missing test result is a lot that can't be claimed, however good the work under it.
What this means for how you run quality
Don't staff QC and call it QA. Plenty of contractors test diligently and still fail the records question, because results live in a technician's inbox and never land against the lot. The fix isn't more testing – it's structure: every result, photo, and sign-off captured against the ITP line and the lot it belongs to, at the time it happens.
In CONQA, the ITP is the working structure of the job. Checklists are completed on site as the QC happens, photos and results attach to the exact item, and the conformance record that supports the claim builds itself as the work proceeds. How it works covers the mechanics.
The record that holds the plan and the evidence together is what gets you paid – book a demo to see it built on work like yours.