For buyers contracting authority
Reach for 48331000 when the deliverable is a project or portfolio management product the authority will run itself, not a service where someone else manages the project. The trigger is the software: a licence, a subscription, or a hosted platform that staff use to plan, schedule and report.
The sibling boundary is narrow but real. Scheduling software (48332000) is the right code when the tool is purely a calendaring or scheduling engine without the wider project and portfolio layer, and contact management (48333000) is a different product class again. Where the package genuinely does both, set the primary CPV code by the dominant function.
The sharper confusion is with services. If the contract buys people to run or advise on a project, that is project management consultancy under the services vocabulary (72224000 for project management consultancy, or the wider 79421000 family), not a software code. Several awards here bundle the licence with configuration and support, which is fine: keep it under 48331000 as long as the packaged tool is the main purpose of the contract.