Most website projects that go badly wrong for accounting and advisory firms go wrong in the first fortnight, before anyone has drawn a screen. The brief was vague, or the designer wrote it, or it never existed at all. You do not need to understand responsive layouts or content management systems to write a good one. You need to know your own practice, and you need to be specific about a handful of things nobody else can tell the designer.

I have read briefs that ran to forty pages and briefs that ran to three paragraphs. The three-paragraph one produced a better website, because it was written by someone who had thought about what the firm needed rather than someone working through a template.
A brief for a three-partner practice in Hamilton is not a request for proposal. It does not need a weighted scoring matrix or a vendor evaluation panel. Those documents exist because large organisations have to demonstrate procurement fairness, and your firm does not have that problem.
Two pages is enough. Who the site is for, what you want it to achieve, what exists already, who is doing what, when you need it, and roughly what you are prepared to spend. A designer reading that can quote accurately. A designer reading forty pages will skim, quote from the parts they understood, and you will find the gap in month three.
Plenty of agencies offer to run a discovery workshop and produce the brief for you. It sounds efficient, and sometimes it is. But a brief written by the firm that will be paid to deliver it tends to describe work that firm is good at. If their strength is visual design, the brief emphasises brand refresh. If they sell retainers, it finds reasons you need a content programme.
This is not dishonesty. It is the ordinary shape of a conversation where one party knows the subject and the other does not.
You know things the designer cannot. That sixty per cent of new clients arrive by accountant referral rather than search. Which two questions every prospect asks on the first call. That the KiwiSaver advice work is the part of the practice you want to grow. None of that is visible from outside, and all of it should shape the site.
"Our clients" is not an audience. Most financial services sites serve at least three groups: existing clients who want a document or a phone number, referred prospects checking you are real before they ring, and cold search visitors who have never heard of you.
Rank them, and say why. That single instruction changes what sits above the fold, whether the site needs a login, and how much of the homepage goes to explaining what you do.
Then name one enquiry goal. Not five. Firms routinely brief a site that must generate enquiries, recruit staff, host client resources, publish thought leadership and support the KiwiSaver arm. A site optimised for five outcomes is optimised for none, and every design argument becomes unresolvable because there is no agreed measure of better. Pick the action you want a stranger to take, write it in one sentence, and let the rest be secondary.
This is the line most briefs skip, and it is the most common reason projects stall. Design is signed off in week four and the site launches in month seven, because nobody wrote the About page.
Say it plainly. Either the firm supplies all copy by an agreed date, or the designer subcontracts a writer at a stated cost, or the existing content is migrated with light editing. Those are three different projects at three different prices, and ambiguity means the designer has quoted for one while you assumed another.
If the firm is supplying copy, be honest about capacity. A partner billing at $300 an hour with a full client load will not write twelve pages of website copy in the evenings. I have watched that assumption cost firms four months.
Financial services sites carry obligations a designer working across restaurants and trades businesses will not know about: disclosure requirements for advice providers, professional body rules on how qualifications are described, and the privacy duties that attach the moment a contact form goes on a page.
Name compliance review as a step in the timeline, with a named reviewer and an allowance of time. Not a vague expectation that someone checks it before launch. If the privacy statement has to reflect what the Privacy Act 2020 requires of the data your enquiry form collects, decide now who writes it and when they see it.
Firms that leave this to the fortnight before launch either delay the launch or ship something they quietly amend later. Both are avoidable with one line in the brief.

Describe the problem and leave the fix alone. "Our clients are mostly over fifty-five and read on iPads" is worth more than "use a large sans-serif font". The first lets a designer solve for legibility across the whole site. The second gets one instruction followed literally and nothing else considered.
Constraints worth stating:
- the brand assets you must keep, and the ones you are happy to lose
- the practice management or portal software the site has to connect to
- anything the previous designer built that you are contractually stuck with
- the internal capability you have for updating the site afterwards
That last one matters more than people expect. A firm with nobody willing to log into a content system needs a different build to a firm with a marketing coordinator. Say which you are. Do not say which platform to use.
Colours, for a start. Unless you have a brand guide you are committed to, specifying a palette removes one of the few things a designer is unambiguously better at than you are.
Homepage image carousels are the other perennial. Partners ask for them because competitors have them. They perform poorly almost everywhere, and a designer who agrees to one without argument has told you something about how they work.
The strongest temptation is to point at another firm's site and say make it like that. Reasonable instinct, bad brief. What you actually mean is more specific - that their site feels more established, or that the team page is one click away. Say the specific thing. Naming a competitor as the target hands the designer a copying exercise and gives you no way to judge whether the result serves your firm.

Partnerships are structurally bad at this. Three partners each review the homepage, each has a different view, and the designer receives three sets of contradictory feedback to reconcile without offending anyone.
Name one approver in the brief. Give them authority over design and copy, and say in writing that other partners' input goes through them rather than direct to the designer. It feels bureaucratic for a small firm. It saves weeks.
State how many revision rounds are included, too. Most quotes assume two. Firms often assume unlimited, discover otherwise at round four, and the relationship sours over an invoice nobody expected. Better to have that conversation while it is a line in a document rather than an argument about goodwill.
"A website" is not a scope. Twelve pages and forty pages are different projects at different prices, and if the brief does not say which, the quote is a guess.
Count what you need. Home, services broken down however the practice is organised, team, about, contact, and whatever compliance pages you are obliged to carry. Then decide separately what happens to the old site - the eighty blog posts from 2018, the profiles of staff who have left, the news item about the office move.
Migrating that content is work. Deleting it has consequences for search traffic and for anyone holding an old link. Either is fine. Not mentioning it means the designer prices a clean build and you discover in month two that your existing content is an extra.
Launch is the middle of the project, not the end. Most briefs stop there, and the ongoing arrangement gets negotiated in the tired week after go-live when nobody has leverage or energy.
Put it in the brief as a question you want the quote to answer. Who hosts the site and what does that cost annually. Who applies software updates, and how often. What happens when the enquiry form stops sending mail on a Friday afternoon, and how quickly. Whether training is included, and for how many staff.
You are not obliged to buy a care plan from whoever builds the site. But know what you will be paying before you choose, because a cheap build with a vague and expensive ongoing arrangement is not the saving it appears to be.
None of this asks you to know how a website is built. It asks you to know your own practice well enough to say who the site is for, what you want it to do, and who is responsible for each part of getting there. The designers worth hiring will be relieved to get a brief like that. The ones who find it constraining have told you something useful.