BRD vs PRD vs SRS: Differences, Templates and When You Need Each

This guide is for founders, product managers, business analysts and procurement teams who are about to commission software and keep hearing three acronyms used as if they were the same thing. By the end you will know what each document contains, who writes and signs it, which one your project actually needs, and you will have section-by-section templates you can copy, including a worked PRD for an AI feature.

What is the difference between a BRD, a PRD and an SRS?

The difference is the question each answers: a BRD answers why and what the business needs, a PRD answers what the product does for users, and an SRS answers precisely how the system must behave, in testable terms.

Aspect	BRD (Business Requirements Document)	PRD (Product Requirements Document)	SRS (Software Requirements Specification)
Core question	Why are we doing this, and what outcome does the business need?	What should the product do for which users?	Exactly how must the software behave?
Typical author	Business analyst or project sponsor	Product manager	Business analyst, solution architect or tech lead
Main readers	Leadership, finance, sponsors	Design, engineering, marketing, support	Developers, testers, vendors, auditors
Language	Business outcomes, money, process	User problems, stories, priorities	Numbered, testable shall statements
Typical length	5-15 pages	5-20 pages	20-80 pages
Changes how often	Rarely after sign-off	Every release cycle	Under formal change control
Good test	Could finance approve the budget from it?	Could design start wireframes from it?	Could QA write test cases from it?

The documents form a chain. Each business goal in the BRD should trace to features in the PRD, and each feature should trace to numbered requirements in the SRS. If a requirement cannot be traced upward, question why it is there.

Is there a standard for requirements documents?

Yes, ISO/IEC/IEEE 29148:2018 is the international standard for requirements engineering, and it describes business, stakeholder, system and software requirements specifications, though it does not define a PRD, which is an industry practice.

The standard is useful for two things even on small projects. First, its list of characteristics of a good requirement: necessary, unambiguous, complete, singular, feasible, verifiable, correct and conforming. Second, its idea that each information item has a defined audience. You do not need to buy and follow the full standard to borrow those ideas. The standard itself is sold by ISO and national standards bodies; the summary on its catalogue page is enough to understand the scope.

The PRD grew up in product companies, where a single team owns a product over many releases. It is lighter, written for a cross-functional team, and expects to change. That is why a PRD and an SRS can coexist: the PRD guides what to build this quarter, the SRS fixes what was agreed with a vendor.

BRD template: sections and what goes in each

A useful BRD fits on 5 to 15 pages and covers the business problem, measurable objectives, scope boundaries, stakeholders, current and future process, high-level requirements, constraints, and the cost-benefit case that justifies spending money.

Section	What to write	Example line
1. Background and problem	What hurts today, with numbers	Order entry takes 11 minutes per order across 3 spreadsheets
2. Objectives	Measurable outcomes and dates	Cut order entry to under 3 minutes by Q2
3. Scope	In scope and explicitly out of scope	Out of scope: payroll, procurement
4. Stakeholders	Who decides, who uses, who is consulted	Sponsor: COO; users: 14 sales coordinators
5. Current and future process	Short as-is and to-be flows	Dealer order arrives by phone, typed twice
6. High-level business requirements	10-30 numbered needs, not features	BR-04: Dealers see live stock before ordering
7. Constraints and assumptions	Budget, deadlines, regulations, systems to keep	Must keep existing accounting package
8. Cost-benefit and risks	Expected saving, payback, top risks	Payback in 14 months on staff time alone

PRD template: sections and an AI feature example

A PRD states the user problem, target users, success metrics, user stories with acceptance criteria, scope for this release, non-goals, design notes and open questions, and it should be short enough that the whole team actually reads it.

PRD sections

1. Problem statement: one paragraph, from the user's side.
2. Target users and jobs to be done: who, in which situation.
3. Success metrics: two or three numbers you will check after launch.
4. User stories with acceptance criteria: as a role, I want, so that, plus given-when-then checks.
5. Release scope and non-goals: what is in this version, what is deliberately left out.
6. Design and content notes: links to wireframes, copy rules, empty states.
7. Dependencies and risks: other teams, data, third parties.
8. Open questions: each with an owner and a date.

Worked example: AI reply suggestions in a support inbox

AI features need extra PRD sections that a classic template misses: what data the model may see, how quality is measured, what happens when the model is wrong, and the cost ceiling per request.

PRD field	Example content
Problem	Agents spend about 40% of their time typing near-identical replies to order status questions
Success metrics	Median handling time down 25%; suggestion acceptance above 50%; complaint rate unchanged
User story	As a support agent, I want a draft reply based on the order record so I can send it after a quick check
Data allowed	Order status, dispatch date, tracking ID; never payment details or other customers' data
Quality evaluation	Test set of 200 past tickets, scored for correctness and tone before launch and monthly after
Failure behaviour	If confidence is low or the order is not found, show no draft rather than a guess
Human control	Agent must click send; no automatic replies in version 1
Cost ceiling	Model cost per suggestion capped; alert if monthly spend crosses the set budget
Non-goals	No refunds, no policy decisions, no languages beyond English in version 1

For a longer walkthrough of the PRD itself, see how to write a product requirement document.

SRS template: sections that make requirements testable

An SRS turns agreed features into numbered, verifiable requirements covering functions, data, interfaces, performance, security and constraints, so a vendor can estimate it and a tester can write a pass or fail case for every line.

Section	Content	Testable example
Introduction and definitions	Purpose, scope, glossary, references	Defines dealer, order, credit limit
Overall description	Users, operating environment, assumptions	Runs in current Chrome and on Android 10 and above
Functional requirements	Numbered shall statements per module	FR-12: The system shall block an order that exceeds the dealer's credit limit
External interfaces	APIs, file formats, hardware	Exports invoices as JSON to the accounting system nightly
Non-functional requirements	Performance, availability, security, accessibility	Order search returns in under 2 seconds for 100,000 orders
Data requirements	Entities, retention, migration	Order history retained for 8 years
Acceptance criteria and traceability	Link each requirement to a BRD or PRD item and a test	FR-12 traces to BR-04 and test TC-31

Our SRS template guide has a full fill-in version.

Which requirements document does your project need?

Choose by risk and contract shape: a fixed-price outsourced build needs an SRS, an in-house product team iterating weekly needs a PRD, and any project asking leadership for a sizeable budget needs at least a short BRD.

Situation	BRD	PRD	SRS
Startup MVP with an in-house team	One page	Yes	No
Fixed-price project with an outside vendor	Short	Optional	Yes
ERP or internal system replacing spreadsheets	Yes	Optional	Yes
Regulated software (health, finance)	Yes	Yes	Yes, under change control
New feature in an existing SaaS product	No	Yes	Only for complex integrations

A simple rule: the further the writer is from the builder, the more formal the document must be. Same room, a PRD and conversation work. Different company and a fixed price, write the SRS.

What we see on real projects at JK Tech Hub

On more than 150 projects since 2018, the most common failure is not a missing document but a document nobody signed, so scope disputes appear in month three when the cost of change is highest.

From our office in Rajkot we build for clients in India, the US, the UK and the Gulf, and the patterns repeat. A manufacturer arrived with a 40-page wishlist that was really a BRD with features mixed in; turning it into a 12-page BRD and a 35-page SRS took two weeks and cut the estimate by about a third because duplicates and nice-to-haves surfaced. A US founder arrived with a strong PRD but no non-functional requirements; we added performance and data retention lines before quoting, which avoided a rework later.

Our practice now: a paid discovery phase of 1 to 3 weeks that produces a signed SRS, a clickable prototype and a fixed quote. Clients keep the documents even if they choose another vendor.

Common mistakes when writing BRD, PRD and SRS documents

The most frequent mistakes are mixing solutions into the BRD, writing PRD stories without acceptance criteria, using vague words such as fast or user-friendly in the SRS, and leaving out what is explicitly out of scope.

• Vague adjectives: replace fast with a number and a condition, such as under 2 seconds at 50 concurrent users.
• Compound requirements: one shall per line, so each can pass or fail on its own.
• No out-of-scope list: what you leave unsaid will be assumed in, by someone.
• No owner for open questions: an open question without a name and a date stays open.
• Documents that never change: a PRD that is not updated after a decision is worse than none.

Related reading and next step

These guides go deeper on each document and on how to work with an outside development team once your requirements are written down and agreed by everyone who will sign off the build:

• SRS template with examples
• How to write a product requirement document
• Connect your Scrum workflow to Git, CI/CD and releases
• Web application development services

Send us your draft requirements through the contact page or WhatsApp and we will return a fixed quote with a gap list.