I've read a lot of requirements documents. Some were 80 pages long and told me almost nothing. Others were three pages in a shared doc and gave me enough to quote the project accurately within a day.
The difference was never length. It was whether the document answered questions or just described screens.
If you're about to hand a project to an agency or an internal team, this is the guide I wish more clients had read first. I'll show you what a useful software requirements document contains, how to scope a software project without pretending you can predict everything, and — honestly — when you should skip the document entirely and just talk to a developer.
First, the uncomfortable truth about requirements
You will get some of it wrong. That's not a failure of effort. It's just how building software works. You learn things in month two that change your mind about decisions you made in month one.
So the goal of a requirements document isn't to be perfectly right. The goal is to make your thinking visible so that when reality pushes back, everyone can see which assumption broke and adjust deliberately instead of arguing.
A good document does three things:
- It lets a developer estimate cost and time with reasonable confidence.
- It records the why behind decisions, so future changes are informed rather than random.
- It makes disagreements surface early, when they're cheap.
That's it. If your doc does those three things in four pages, you're done. Stop writing.
Start with the problem, not the solution
The single most common mistake I see: the document opens with a feature list. "Admin dashboard. User roles. Reporting module. Email notifications."
I now have no idea what any of that means, because I don't know what you're actually trying to fix.
Open instead with something like this:
"Our sales team of 11 people tracks leads in a shared spreadsheet. Roughly a third of enquiries never get followed up because nobody knows who owns them. We want every enquiry to have a clear owner and a next action date, and we want the sales manager to see what's slipping without asking people."
Now I understand the shape of the thing. I can also tell you honestly whether you need custom software at all — which brings me to my next point.
Write down what "better" looks like
Before features, define outcomes. Not vanity metrics. Real, observable changes:
- "No enquiry sits unassigned for more than 4 hours."
- "Monthly reporting takes 20 minutes instead of two days."
- "Warehouse staff stop re-entering the same order into two systems."
These become your acceptance criteria later. They also protect you from feature creep, because every proposed addition can be tested against them: does this move one of those numbers?
How to scope a software project without guessing
Scoping is where most budgets quietly explode. Here's the sequence I use when a client asks me how to scope a software project properly.
1. List the users, then the jobs
Write down every type of person who touches the system. Not roles in an org chart — actual distinct behaviours. A "manager" who only views reports is a different user from a "manager" who approves refunds.
Then, for each one, list the jobs they need to get done. Short sentences. "A sales rep needs to log a call and set a follow-up date in under 15 seconds." That last part — the constraint — is gold. It tells me the interface matters more than the data model here.
2. Map the flows, not the screens
Screens come from flows, not the other way round. Describe the journey: enquiry arrives → assigned to rep → rep logs contact → outcome recorded → either converted or archived with a reason.
Once the flow is written down, designers and developers can propose fewer, smarter screens than you would have specified. That's the point of hiring them.
3. Be brutally explicit about integrations
This is where estimates go wrong most often. Every external system you touch is a source of hidden work: authentication, rate limits, data mismatches, someone else's downtime.
For each integration, note: which system, which direction data flows, how often, and whether you have API access and credentials today. If the answer to that last one is "we'll have to ask the vendor," flag it as a risk. I've seen two-week features become two-month features because a legacy ERP only exported CSVs over FTP at midnight.
4. Separate must-have from must-have-eventually
Use three buckets. Version 1, Version 2, and Not Now. Force yourself to put things in Not Now. If everything is Version 1, you don't have a scope — you have a wish list, and you'll ship late.
A useful test: if we launched without this feature, would a real user be unable to complete their core job? If they'd merely be annoyed, it's Version 2.
5. Write down the non-functional stuff
Boring, but this is what determines architecture and therefore cost:
- Scale: how many users, how many records, how fast is it growing?
- Availability: is 30 minutes of downtime a shrug or a crisis?
- Compliance: GDPR, HIPAA, data residency? Say so now, not after we've picked a database region.
- Devices: desktop only, or do field staff need this on a phone with patchy signal?
- Who maintains it: your team, or ours? This changes technology choices.
What to leave out of a software requirements document
Restraint is a skill. Things I'd generally cut:
- Prescribed tech stack — unless you have a real constraint like an existing team or an approved vendor list. Otherwise you're limiting options for no benefit.
- Detailed UI specifications — colours, button placement, pixel widths. Describe intent and constraints; let design happen in design.
- Database schemas — unless you're integrating with something existing that dictates them.
- Filler sections — glossaries nobody reads, revision histories with one entry, a page of mission statement.
When you don't need a formal document
Let me argue against my own topic for a second.
If you're building a small internal tool, a landing page with a form, or a prototype to test an idea, a full requirements document is a waste of your time. A one-page brief plus a 45-minute call will get you further. Write the problem, the users, three or four flows, and your budget ceiling. Then talk.
Similarly, if you're solving a well-understood problem, check whether an existing product does it before commissioning anything. Plenty of teams have paid for a custom CRM that a configurable one would have handled for a fraction of the cost. That's part of why we built Orbis Lead CRM — for a lot of sales teams, the honest answer is "you need lead ownership and follow-up discipline, not a bespoke system." Custom software earns its keep when your process is genuinely a competitive advantage, or when nothing off the shelf fits your workflow without painful compromise.
A lean template you can copy
Here's the structure I'd use for most mid-sized projects. Aim for 5–12 pages, not 50.
- Problem statement — what's broken today, in plain language.
- Success criteria — 3 to 5 observable outcomes.
- Users and their jobs — one short list per user type.
- Core flows — step-by-step journeys for the 4 or 5 things that matter most.
- Scope buckets — V1 / V2 / Not Now.
- Integrations — system, direction, frequency, access status.
- Non-functional requirements — scale, uptime, compliance, devices, maintenance.
- Constraints — budget range, hard deadlines, existing tech you must live with.
- Open questions and risks — the most valuable section, and the one most people skip.
That last section deserves a note. Listing what you don't know signals maturity, not weakness. When a client hands me a doc with "we're unsure whether customers will accept online payment — needs validation," I immediately trust the rest of the document more.
Treat it as a living artefact
Put the document somewhere editable and shared, not in an email attachment named final_v4_REVISED. Review it at the end of every sprint or milestone. When something changes, change the doc and note why. Six months in, that trail of reasoning is worth more than the original text.
And expect the document to shrink over time, not grow. As decisions get made and built, they move out of "requirements" and into "the software."
If you want a second pair of eyes on a scope before you commit budget to it, I'm happy to look. We do this often — sometimes the outcome is a proposal, sometimes it's us telling you the project is smaller than you thought, or that a product you can configure will do the job. Either way you'll leave the conversation with a clearer plan. You can see our work for context, or just get in touch and send over whatever you've got, even if it's rough notes.