A client onboarding questionnaire is the structured set of questions you send a new client immediately after they sign, to collect everything you need before work starts. Done well, it replaces three discovery calls and a month of email. Done badly, it is a 40-field form that gets half-completed and abandoned.
The difference is not length. It is whether each question changes what you will actually do. The questionnaire below is grouped into seven sections, and every question carries a short note explaining what you do with the answer. Delete any question where that note does not apply to your engagement.
The rule that makes intake forms work
Never ask a client something you can find out yourself. Their company address, their staff count, their current website platform, their competitors' ad copy: all of that is findable in five minutes. Every question you ask that you could have researched spends the client's patience on something that does not need it, and patience is finite. Spend it on the things only they know.
The second rule: ask for decisions, not data. "What is your budget?" gets you a number that may be fiction. "If this works, what would you want to spend next quarter, and who signs that off?" gets you a decision-maker and a real constraint.
How to send it
Send it once, in one place, with a deadline, alongside the file requests and access requests. Splitting intake across a form, an email thread, and a shared folder is the single most common reason onboarding stalls. If you can, send it as part of the same link that carried the proposal, so the client is not tracking four destinations.