What is Functional Requirements? — UK Software Development Guide

4 min readJune 2025ClickMasters Technical TeamReviewed by James Whitmore, CTO
what are functional requirements software

Direct Answer

Functional requirements describe what a software system must do — the specific behaviours, functions, and capabilities the system must provide. Examples: "A user must be able to register with their email address and password," "The system must send a confirmation email within 60 seconds of registration," and "The admin must be able to export user data as CSV." Functional requirements contrast with non-functional requirements (which describe how the system should perform).

Functional-requirements in the UK

Functional requirements are the core output of ClickMasters' Technical Discovery phase — typically expressed as user stories with acceptance criteria. For UK fixed-price contracts, precisely defined functional requirements prevent scope disputes: a feature not described in the agreed requirements is not in scope. UK GDPR adds specific functional requirements to most software projects: consent capture, data subject rights (access, erasure, portability), and audit logging are functional requirements driven by regulation rather than business preference.

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