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GuideOctober 5, 20266 min readByte Operator Team

How to Write a Software Requirements Document (SRS) — Free Template & Examples

Learn how to write a clear software requirements specification that developers can estimate and build from. Includes a section-by-section template, user story and acceptance criteria examples, MoSCoW prioritisation and common mistakes.

Software requirements document with user stories, acceptance criteria, wireframes, flow diagram and MoSCoW scope cards

Most software projects that run over budget do not fail because of bad code. They fail because nobody wrote down clearly what the software should do. A good software requirements document (often called an SRS — Software Requirements Specification) turns ideas into something a team can estimate, design, build and test.

You do not need a 100-page specification. You need a focused document that answers the right questions. This guide shows you exactly what to include, with examples you can copy.

1. What a Requirements Document Is (and Is Not)

  • It is: a shared agreement about the problem, the users, what the system must do, and how you will know it works.
  • It is not: a technical design. Describe what and why; let your engineers propose how.
  • It is a living document: in agile projects the core goals stay stable while detailed stories are refined sprint by sprint.

2. Software Requirements Document Template (Section by Section)

1) Overview and business goals

Two or three paragraphs on the problem and measurable success criteria. Example: "Customers currently request quotes by email, taking 48 hours on average. The portal should let them get an instant quote online, cutting response time to under 5 minutes and increasing quote-to-order conversion by 20%."

2) Users and roles

List every user type and what they can do: Customer, Sales Rep, Admin, Finance. Include rough numbers (e.g. 2,000 customers, 15 internal staff) — these affect architecture and cost.

3) Scope: in and out

The "out of scope" list is just as important. It prevents assumptions and protects your budget. Example: "Out of scope for v1: mobile apps, multi-currency, integration with the legacy warehouse system."

4) Functional requirements (user stories)

Write features as user stories with acceptance criteria so they can be tested:

User story:
As a returning customer,
I want to reorder a previous purchase in one click,
so that I can restock without searching the catalogue again.

Acceptance criteria (Given / When / Then):
- Given I am logged in and have at least one past order,
  When I open "Order history",
  Then each order shows a "Reorder" button.
- Given an item from the old order is out of stock,
  When I click "Reorder",
  Then the remaining items are added to my cart
  And I see a message listing the unavailable item.

5) Non-functional requirements

CategoryExample requirement
PerformancePages load in under 2.5s (LCP) on a mid-range mobile on 4G
ScalabilitySupport 500 concurrent users at launch, 5,000 within 12 months
Availability99.9% uptime, excluding scheduled maintenance
SecuritySSO for staff, MFA for admins, encryption at rest and in transit
ComplianceGDPR: data export and deletion on request
AccessibilityWCAG 2.2 AA
Browser/device supportLatest two versions of Chrome, Safari, Edge, Firefox; iOS and Android

6) Integrations and data

List every external system (CRM, payment gateway, ERP, email provider), the direction of data flow, and who owns API access. Note any data that must be migrated from existing systems and its volume.

7) User flows and wireframes

Low-fidelity wireframes or simple flow diagrams for the key journeys (sign-up, checkout, core task) remove more ambiguity than pages of text.

8) Assumptions, constraints and risks

Budget limits, fixed deadlines, required technologies, third-party dependencies and anything still unknown.

3. Prioritise with MoSCoW

Label every requirement so the team knows what can move if time or budget gets tight:

  • Must have — the product does not work or launch without it.
  • Should have — important, but there is a temporary workaround.
  • Could have — nice to have if time allows.
  • Won't have (this time) — explicitly deferred to a later release.

A healthy first release keeps "Must haves" to roughly 60% of the estimated effort, leaving buffer for the unexpected. This is the core idea behind a lean MVP.

4. Common Mistakes to Avoid

  • Vague words: "fast", "user-friendly", "secure". Replace them with measurable targets.
  • Prescribing solutions: "Use a dropdown" instead of "Users need to select one of 40 regions quickly".
  • Missing edge cases: What happens when payment fails, a user has no data yet, or an upload is too large?
  • No owner for decisions: Name one product owner who can answer questions and approve changes.
  • Forgetting admin and reporting: Back-office screens and exports are often 30% of the effort.
  • Writing it alone: Review with real users and at least one engineer before finalising.

5. Quick Requirements Checklist

  1. Problem and measurable goals are defined.
  2. All user roles are listed with permissions.
  3. In-scope and out-of-scope lists are written.
  4. Every feature has a user story and acceptance criteria.
  5. Non-functional requirements have numbers.
  6. Integrations and data migration are documented.
  7. Key flows have wireframes.
  8. Everything is prioritised with MoSCoW.
  9. A single decision-maker is named.

Not sure where to start? ByteOperator runs structured discovery workshops that turn your idea into a clear, estimate-ready specification. Explore our MVP development and custom software development services, read how to choose a development partner, or talk to our team.

Related reading:

Frequently asked questions

What is the difference between functional and non-functional requirements?

Functional requirements describe what the system does, such as "users can reset their password by email". Non-functional requirements describe how well it does it, such as performance, security, availability, accessibility and scalability targets.

How long should a software requirements document be?

Long enough to remove ambiguity and no longer. For an MVP, 8 to 20 pages including user stories and wireframes is typical. Large enterprise systems need more, but they are usually split into separate documents per module.

Do agile teams still need a requirements document?

Yes, but a lighter one. Agile teams keep a stable overview of goals, users, scope and non-functional requirements, then maintain detailed user stories in a backlog that is refined each sprint rather than fully specified upfront.

What is MoSCoW prioritisation?

MoSCoW is a prioritisation method that labels each requirement as Must have, Should have, Could have or Won’t have this time. It makes trade-offs explicit so a team can protect the launch date and budget by moving lower-priority items to later releases.

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