Begin with the problem you are solving, not a feature list. Which people will use it day to day, how often, and what does the process look like without it? An estimator who knows what you are trying to achieve can propose a simpler way to reach it; a team that receives only a feature list will price the list as written.

Describe the scope as user stories or scenarios: a walk through each important path. Equally important, list what the first release deliberately excludes. An explicit exclusion list removes more friction later than almost anything else in the document. Mark too which parts are firm and which are still under discussion — honest teams price those differently, and hiding it helps nobody.

Write down the hard constraints. These include systems you must integrate with, the data you already hold and its condition, regulatory obligations, expected load, supported browsers or devices and any technology you are committed to. Where a date is genuinely fixed, say what depends articles on software outsourcing it: a good team can often rearrange the plan to meet it, but not if the date is a secret.

Write down what the word done means for each item. Clear acceptance criteria need not use special syntax: a plain-language note stating the expected behaviour will do. This single habit reduces the sign-off process by a surprising margin and removes the usual argument at handover.

Finally, state what you want in the response. Require a breakdown by feature or module, the assumptions behind each number, the risks the team sees and ongoing software support company a low number and a high number. Treat a wide range as useful information rather than evasion: it normally identifies where your description is thin. From there tighten that section and ask for a new estimate — the second estimate is far closer to reality.