Start With the Document in Front of You
If you are sitting with a requirements document open and asking yourself whether what you have just written is a business requirement, a functional requirement, or a technical requirement, you are doing exactly the right thing. Mixing up business vs functional vs technical requirements is one of the most common problems I see in documentation reviews, and it causes real downstream pain: developers building the wrong thing, testers not knowing what done looks like, and stakeholders approving documents they do not actually understand.
The good news is that once you have a clear mental model for each layer, the sorting becomes fast. I am going to give you that model, show you where each type lives in your documentation, and walk through a real example where the lines got blurry and pushed back.
The Three Layers and What Each One Actually Means
Think of requirements as three concentric circles. Business requirements sit on the outside: they describe the problem, the goal, or the outcome the organisation needs to achieve. Functional requirements sit in the middle: they describe what a system or solution must do to meet the business need. Technical requirements sit at the centre: they describe how the solution must be built, configured, or constrained to function correctly in its environment.
None of these layers overlaps cleanly in practice, which is why confusion happens. Here is a clean reference table to pin to your screen while you are writing.
| Requirement Type | The Question It Answers | Written By | Lives In | Audience |
|---|---|---|---|---|
| Business Requirement | Why does this project exist? What outcome must be achieved? | BA with sponsor input | BRD or Vision/Scope document | Sponsors, senior stakeholders, project board |
| Functional Requirement | What must the system do to satisfy the business need? | BA with SME and user input | FRD or user stories / use cases | Developers, testers, product owners |
| Technical Requirement | How must the solution be built, hosted, or constrained technically? | Solution architect or technical BA | Technical specification or system requirements | Developers, infrastructure, security |
Business Requirements: The Why Layer
Business requirements describe the need, not the solution. They are outcome-focused and belong at a level where a senior stakeholder who has never touched the system can read them and nod in recognition. If your business requirement mentions a button, a field, a database, or a workflow, it has slipped into functional territory.
On Project X, a government employment programme I worked on, the vision/scope document captured the following as a business requirement: the programme team needed to effectively manage data for monitoring and evaluation purposes, gain administrative efficiencies, and improve customer service capabilities. That is a business requirement. It says nothing about how those goals will be achieved. It simply states what success looks like for the organisation.
Business requirements typically emerge from conversations about strategy, compliance obligations, pain points in current operations, or external funding conditions. I always trace them back to a named business driver. If you cannot point to a driver, the requirement is probably too vague to be actionable. You can read more about that framing in this article on business driver examples and how to align ICT projects with strategic goals.
Functional Requirements: The What Layer
Functional requirements describe what the system must do in response to the business need. They are specific, testable, and written at a level where a developer can understand exactly what behaviour is expected. Each functional requirement should trace back to at least one business requirement. If it does not, ask why it is in scope at all.
On the same project, once the business goal of managing referral data was established, the functional requirements described things like: the ability for referral agency staff to complete and submit a referral form via the web system; automated notification to programme staff when a referral was submitted; and the ability to re-submit an amended referral form if follow-up information was required. Those are functional requirements. They describe system behaviours, not business goals.
Notice the shift in language. Business requirements use words like “manage,” “improve,” and “achieve.” Functional requirements use words like “shall,” “must,” “display,” “submit,” “notify,” and “validate.” That language shift is your first signal that you have moved from one layer to the next.
For a deeper look at the structural difference between the documents that house these two types, the article on Business Requirements Document vs Functional Requirements Document covers the format and content distinctions in detail.
Technical Requirements: The How Layer
Technical requirements describe the constraints and characteristics of the solution itself, independent of any particular user action. They answer questions like: what browser versions must be supported, what data encryption standard must be applied, how many concurrent users must the system handle, and what integration protocols must be used.
On Project X, the operational requirements documented that the system must support up to 25 concurrent users, and a separate constraint noted that personal and sensitive client information must be managed in accordance with applicable government privacy principles. The privacy compliance requirement sits at the boundary between a business constraint and a technical requirement. It was driven by regulation (a business reason) but had direct implications for how the system was designed (a technical concern). In practice, I documented it in both places and flagged the link explicitly.
Technical requirements are often written or at least reviewed by a solution architect. As a BA, my job is to ensure they exist and are traceable, not necessarily to author them in full. What I never do is leave them undocumented because “the developers will figure it out.” That assumption is where security gaps, performance failures, and integration surprises come from.
A Concrete Example Where the Lines Got Complicated
Let me walk you through a situation that took more than one conversation to resolve. On Project X, one of the programme’s grantee organisations needed to submit monthly reports on a case-by-case basis for every family they were supporting, with the report due by the tenth of the following month. Simple enough on the surface.
The programme manager wanted this captured as a single business requirement: “Grantees will report progress on a monthly basis.” The ICT team lead took that as licence to build a simple upload form with no validation or deadline logic. When I pushed back and said we needed to specify what the system must do to enforce the deadline and validate the content of the submission, the ICT team lead argued that was “implementation detail” and outside my scope as a BA.
This is a friction point I have encountered many times. The resolution was to break the requirement into three explicit layers in the documentation:
- Business requirement: Grantee service provision must be monitored through structured monthly reporting to support programme oversight and evaluation.
- Functional requirements: The system must allow a Grantee Case Manager to complete and submit a monthly family service report; it must display a due date based on the reporting period; it must notify programme staff when a report is submitted; and it must allow programme staff to flag reports for follow-up and log actions taken.
- Technical requirement: The system must enforce role-based access so that only users attached to a specific grantee organisation can submit reports for that organisation’s cases; report submission timestamps must be recorded in the audit log.
Once the layers were separated and documented that way, the ICT team lead acknowledged that the functional requirements had been genuinely missing from their build scope. The rewrite of the functional specification took an additional two days, but it prevented a much larger rework later when the reporting workflow went into testing.
How to Decide Which Layer a Requirement Belongs To
When I am unsure where a requirement sits, I work through three quick questions in order.
- Does it describe an organisational outcome or a problem to solve? If yes, it is a business requirement. Write it in the BRD or the vision/scope section of your project documentation.
- Does it describe a behaviour, action, or response that the system must perform? If yes, it is a functional requirement. Write it in the FRD or express it as a user story with acceptance criteria.
- Does it describe a constraint on the technology, infrastructure, or technical design? If yes, it is a technical requirement. Write it in the system requirements or technical specification, and link it to the functional requirement it supports.
If a requirement seems to touch more than one layer, that usually means it contains multiple requirements bundled together. Split them. A single bundled requirement is one of the fastest ways to lose traceability in your documentation. A requirements traceability matrix becomes almost impossible to maintain when requirements are compound.
Where Each Type of Requirement Lives in Your Documents
The table above pointed to the document homes for each type, but it is worth being explicit about what goes where in practice, because different organisations use different naming conventions.
- Business Requirements Document (BRD): This is where business requirements live. It captures the problem, the scope, the business goals, the benefits, and the high-level constraints. It should be readable by executives who will never open the FRD.
- Functional Requirements Document (FRD) or user stories: This is where functional requirements live. On waterfall projects, these go into an FRD. On agile projects, they appear as user stories with acceptance criteria, use cases, or process flows. Either way, they describe system behaviour.
- System Requirements Specification (SRS) or technical specification: This is where technical requirements live. Some organisations include a technical requirements section at the back of the FRD. Others maintain a separate document. What matters is that they are explicit and traceable.
If your organisation uses a single combined document, as some smaller projects do, clearly label each section so the reader knows which layer they are looking at. Mixing layers without labels is the documentation equivalent of putting raw ingredients, instructions, and the finished dish all on the same plate.
The reason layering your requirements correctly matters is not bureaucratic tidiness: it is about giving each audience exactly what they need to do their job. A sponsor reading your business requirements should feel confident the project is solving the right problem. A developer reading your functional requirements should know exactly what to build. An architect reading your technical requirements should know exactly what constraints to design within. When those three audiences can each read their layer without confusion, your documentation is working. Getting there reliably is a skill that comes from practice and from treating the separation as deliberate craft, not administrative overhead.
Frequently asked questions
What is the difference between business requirements and functional requirements?
Business requirements describe the outcome or goal the organisation needs to achieve, without specifying how the solution will work. Functional requirements describe what the system must do to deliver that outcome. A business requirement says why the project exists; a functional requirement says what the system must do in response.
What are technical requirements in software development?
Technical requirements describe how the solution must be built, hosted, or constrained at a technology level. They cover things like performance thresholds, security standards, integration protocols, supported browsers, and concurrent user limits. They are distinct from functional requirements, which describe system behaviour rather than technical design.
Where do business, functional, and technical requirements go in documentation?
Business requirements belong in a Business Requirements Document or vision/scope document. Functional requirements belong in a Functional Requirements Document or as user stories with acceptance criteria. Technical requirements belong in a system requirements specification or technical design document, and should be traceable to the functional requirements they support.
How do I tell if a requirement is functional or technical?
Ask whether the requirement describes something a user or the system does in response to an action, or whether it describes a constraint on how the technology must be built. If it is about system behaviour visible to a user or a process, it is functional. If it is about infrastructure, security standards, or technical design constraints, it is technical.
Can a requirement be both a business requirement and a technical requirement?
A single statement can touch both layers when it is driven by a business rule but has direct technical implications, such as a data privacy obligation that must be enforced through system access controls. In that case, document it in both layers and link them explicitly so the traceability is clear.
Try Ash, Your Virtual BA
If you are sitting with a requirements document and still unsure whether what you have written belongs in a BRD, an FRD, or a technical spec, Ash can help you work through it in real time. Ash is a virtual BA assistant built specifically for this kind of requirements work: it can help you draft layered requirements, check whether your functional requirements trace back to a business need, and guide you through producing a complete BRD or FRD from scratch. Give it your project context and see how quickly the structure falls into place. Try Ash Virtual BA.
Further reading
- 4.4 Understanding Requirements and Designs | The International Institute of Business Analysis™
- Creating clear project requirements
Written by Sam Cordes, founder of the Business Analyst’s Toolkit.