A task is finished when you won't have to handle it again. Not when you did it and not when you handed it over, but when it won't come back to you. And according to the source, when things stay open, it's almost always for one of three reasons you can name.
What finished actually means
The source starts somewhere unexpected, with the word ability, and gives it a definition that changes what the word means. Under this definition, ability isn't measured by how much you know, but by how many things you've closed. In the source, what makes an executive succeed is being able to complete cycles of action fast, and the word that carries the weight is complete.
A cycle of action is anything that begins and needs to end: a quote, an installation, a reply to a customer. And ability, in the source's definition, means completing that cycle, “to handle the matter so it does not have to be handled again.”
The important part is the end of that line. It's the difference between finished and I did it. A job you delivered that will come back for rework isn't finished yet. A reply you sent that will bring another question with it isn't finished either.
The test isn't what you did. The test is whether it comes back.
Suppose an installer wraps up a job and doesn't check it. Over the next two weeks he drives back to the customer twice more, for that same job. As far as he was concerned, the installation ended on day one. In reality it didn't end until the third visit.
Or a business owner who sends a quote without a final price, hoping to speed things up. The quote brings four more messages behind it. Once he adds a price line and an expiry clause, the very same quote brings no follow-up messages at all.
Three reasons something stays open
The source lists three reasons, and the third is the one nobody likes to admit.
The first: nobody grasped that it mattered. In practice it sounds like, I didn't know this was urgent. Someone who doesn't know what happens if the thing isn't done feels no pull to close it.
The second: the cycle itself isn't fully understood. The work got done partway, and whoever did it believed it was complete. Suppose an owner asks an employee to tidy the warehouse. The employee tidies a single shelf and is sure he's done, because nobody ever told him what a tidy warehouse looks like.
The third: hiding that it isn't done. The source describes noncompliance and false reports used as self-protection, in the hope that nobody will notice.
Still, that third reason doesn't have to be a lie. Usually it's hope, the hope that if nobody asks, it will work itself out somehow. Suppose a bookkeeper asks whether something was handled, and hears yes. Two weeks later it turns out that yes meant I started.
Splitting it into three matters because each reason calls for a different response. A task left open because nobody saw why it mattered, and a task left open because someone is hiding it, look the same from the outside. They aren't the same problem.
What an interruption does to what's begun
The other side of the picture is interruption. According to the source, only the most violent emergency justifies pulling someone off a cycle of action, and even then he should go back to it once the emergency is handled.
The source's next line is even harsher: “To completely wreck an area all one has to do is interrupt all cycles begun.” Wreck, not slow down.
And that holds even when the interruption comes from you. Every time you stop something halfway through to check a message, you do exactly this to yourself.
The source also explains why it happens. People get pulled off jobs when whoever is in charge of them doesn't know which jobs are underway. In a small business this hits you in particular, because you run the work and do the work at once, and you can lose track of which thing you're in the middle of.
Suppose a contractor who gets pulled away from the job in front of him by every phone call. By the end of the day he has six starts and zero finishes.
There's a smaller fix too. Suppose a designer who, before answering the phone, writes on a sticky note what she's in the middle of. When she comes back, it takes her seconds instead of minutes to pick it up.
And the bigger opposite is that same contractor, once he sets himself two phone-free hours a day. In those two hours more gets done than in the whole rest of the day.
What the booklet has on this
The chapter this article draws on includes two exercises: the finishing condition, and the interruptions. It also has a self-check, and it's part of a full booklet on what eats a business owner's day, and why.
Next time you mark something as done, it's worth asking one question: will this come back to me?