This is the structure we use when we write requirements with a client during discovery. It is deliberately plain. Each section below says what goes in it and gives a short example, so you can copy the headings into your own document and start filling them in today.
Two habits make it work. Write what happens and who it happens to, instead of qualities like "user-friendly". And wherever a rule feels fuzzy, give a real example with real numbers.
1. Purpose and people
One paragraph on what the product is for, then a list of everyone who uses it and what each of them needs from it.
2. Workflows
Describe each workflow as a sequence: who does what, when, and what must be true afterwards. One workflow per heading.
3. Rules, with worked examples
Every business rule that could be read two ways gets at least one worked example, and ideally one awkward edge case.
4. Edge cases
A list of every "but sometimes" your team can remember. Ask the person who handles the difficult phone calls.
5. The never-list
What the system must refuse to do. These feel obvious from inside the business, which is exactly why they get lost.
6. Priorities
Mark every feature as must-have for launch or later. The first column is the build. The second column is the roadmap.
7. Open questions
Everything you are not sure about, written down next to the name of the person who can answer it. An open question on paper is cheap. The same question discovered halfway through the build is expensive.
Why the template looks like this
Discovery: we write this document with you
Fill in what you can, then bring it to a 30-minute intro call with Alexandru. Even a rough first page makes the conversation more useful.