Take-home tasks: how much time to give, and when it's unpaid work

Why companies set them

CVs lie, interviews don't reveal everything, and hiring the wrong person is expensive. A take-home is an attempt to see how you write code when nobody is watching over your shoulder.

That's reasonable. What isn't is asking for a slice of the actual product under the guise of assessment.

Signs of a reasonable task

Time-boxed. Stated honestly: "designed to take four hours".
Detached from the product. A synthetic problem, not something shipping next week.
Clear criteria. It says what will be assessed.
Not the first step. A conversation first, then the task. A take-home arriving before any contact means you aren't valued much.

Signs you're being used

Several days of work. No assessment requires three days.
A task lifted from the real product. Especially when the wording reads like a ticket.
A finished service is demanded. With deployment, tests, documentation and permissions.
They refuse to discuss reducing the scope.
No feedback on the result. A good sign the result wasn't the point.

How much time to give

What was stated, plus a little. Twenty hours on a four-hour task counts against you: fitting the box is part of the assessment.

If you can't finish, submit the working part and say what's missing and how you'd complete it. That's a normal and respected answer.

Declining politely

Directly, without accusations:

Thanks for the task. By its scope it looks like several days of work, and I'm currently in processes with other companies. Instead I could show you a project of mine where I solved similar problems and walk through the code on a call — you'd see the same thing. Link.

Half of companies agree. The other half aren't ones to regret.

What to attach

A short note: what's done, how to run it, which decisions you made and why, what you didn't get to and how you'd finish. Three paragraphs.

It's what separates a candidate who thinks from one who merely wrote code. And almost nobody does it.

What you can offer instead

Your own finished project — especially a team one, where how you work with people is visible. If your contribution was described not by you but by the person you worked with, with the change history beside it, that answers exactly the question a take-home is set to answer: can you really do this.