Start with the problem you are solving, not a list of screens. Who will use the system, how often, and how is the job done today? A vendor who understands the goal will suggest an alternative that costs less; a team that receives only a feature list will price exactly what you asked for.

Define what is included as user stories or scenarios: who does what, and what happens next. Every bit as useful, state explicitly what is out of scope. An explicit exclusion list removes more argument later than almost anything else in the document. Mark too which items are decided and which are still open — the difference changes the price, and pretending everything is fixed helps no one.

Set out your constraints. This means systems you must integrate with, the data you already hold and its condition, regulatory obligations, expected load, supported browsers or devices and infrastructure that is already decided. Where a date is genuinely fixed, say why: an experienced team can often resequence the work to hit it, angular development company provided they hear about it early.

Write down what done means for each item. Acceptance criteria do not require formal language: a short list setting out what a user should be able to do will do. This one section shortens the review at the end dramatically and eliminates most late-stage disagreement.

Finally, ask for a specific format. Ask for a breakdown by feature or module, a written list of assumptions, fintech software development the risks the team sees and an optimistic and a pessimistic figure. Read a wide range as a signal about the brief: it normally identifies where your description is thin. Then tighten that section and ask again — the next version will be the one worth planning around.