For buyers contracting authority
Pick 72266000 when the deliverable is advice, not software. A contracting authority uses it to buy an architecture review, a build-versus-buy assessment, a platform or supplier evaluation, or specialist input before committing to a larger programme.
The boundary that trips authorities is 72262000: if the contract's main output is working software, that is development, even when advice is part of the job. Reserve 72266000 for engagements where the report, the recommendation, or the design is what gets accepted and paid for.
Two more neighbours matter. Systems consultancy (72246000) is the right pick when the advice spans hardware, networks and integration rather than the software layer alone, and Systems and technical consultancy services (72220000) is the broader parent. Where a single contract folds advice into a larger delivery, set the primary CPV code by the dominant deliverable, not by the whole bundle.