You send the same document to three suppliers and get back numbers that differ by a factor of four. The usual conclusion is that one of them is expensive and one is cutting corners. Occasionally that is true. Far more often all three have priced honestly, and priced three different projects.

The brief is what let them. This is about the specific ambiguities that suppliers resolve in their own favour, and how to close them without writing a specification you are not qualified to write.

Where the factor of four comes from

Take a line most briefs contain: "the site should integrate with our CRM".

One supplier reads a contact form that posts a lead into a CRM inbox. A day of work. Another reads a two-way sync of customers, orders and support history, with conflict resolution and a replay mechanism for when the CRM is down. Six weeks. Both are defensible readings of the same eleven words, and neither supplier is being dishonest.

Almost every large quote gap traces back to a sentence like that. The supplier who read it narrowly wins the work, discovers the real requirement in month two, and raises a change request. The one who read it properly looked expensive and lost. The brief selected for optimism.

A brief is not a specification

The most common overcorrection is to write the solution. Page counts, field lists, a sitemap, sometimes a technology. This produces comparable quotes and a worse project, because you have now bought your own guesses and paid a supplier to implement them.

The distinction that works: describe the problem and the constraints exhaustively; describe the solution only where the decision is genuinely already made.

If the CRM is non-negotiable, say so - that is a constraint, not a solution. If you have decided on a particular CMS because your team already runs three of them, say so and say why. What you should not do is invent a technical answer to look prepared. A good supplier will tell you when your stated solution is wrong; a mediocre one will build it and invoice you.

The six things that actually move the number

In our experience these six account for most of the variance between quotes. Everything else is rounding.

  1. Integrations, named and characterised. Not "integrates with our systems". Which system, which version, does it have an API, who owns the credentials, is it read-only or two-way, and what happens when it is unavailable. This single item explains more quote variance than the other five together.
  2. Content: who produces it, and how much exists. A rebuild of 40 pages you will rewrite is a different project from a migration of 4,000 pages that must survive intact. Say which, and say who is writing.
  3. Who has to be able to edit it afterwards. A site maintained by a developer and a site maintained by a marketing coordinator are different builds. The second costs more and is usually the right answer.
  4. The non-functional requirements you actually have. Accessibility obligations, performance targets, uptime, data residency, security review, procurement standards. These are cheap to design in and expensive to retrofit, and a supplier who does not know about them will not price them.
  5. Volume and scale, in numbers. Products, users, orders per day, peak traffic, languages. "Large" is not a number, and every supplier will assume the number that suits them.
  6. What happens after launch. Are you buying a project or a relationship? A team that expects to maintain the result builds it differently from one that expects to hand it over and leave.

Write down what you do not know

This is the part people leave out, and it is the most useful section in the document.

A brief that says "we do not know whether the ERP can expose stock levels; finding out is part of the work" gets you three quotes that all price the same discovery. A brief that stays silent gets you one supplier who assumed it is easy, one who assumed it is hard, and one who quoted for finding out and looked expensive for doing the right thing.

Uncertainty is not a weakness in a brief. It is the thing that lets suppliers price the same project.

Ask for the same shape of answer

Comparable quotes need a comparable format. Ask every supplier for the same five things, and say you will not be comparing on the headline number alone.

  • A breakdown by phase, with an effort range rather than a single figure, and the assumptions each range depends on.
  • What is explicitly out of scope. This is more informative than the scope.
  • What they need from you, and by when. A quote that assumes zero client time is wrong.
  • The five-year cost, not the build cost: licences, hosting, maintenance, and the support arrangement.
  • One thing in the brief they think is a mistake. The answers to this question separate the suppliers faster than anything else in the process.

Reading the answers

The cheapest quote is informative, but not in the way it looks. Read it for what it left out, then ask the other suppliers whether they would have quoted the same on that reading. Usually they would have quoted less than the cheap one.

The most useful signal is the questions you get back before the quote. A supplier who asks nothing has either done this exact project before - ask them - or is not thinking about yours. A supplier who comes back with six specific, uncomfortable questions is showing you what working with them is like.

And if all three quotes are similar, the brief did its job. That is the whole point of writing one.